FR3044369A1 - SENSOR ASSEMBLY FOR HYDRAULIC CONTROL DEVICE - Google Patents

Abstract

The invention relates to a sensor assembly (1) for a hydraulic control device (10) intended to be arranged in a through passage (15) formed in a wall of the cylinder body and opening into the hydraulic chamber, the sensor assembly (1) comprising: a sensor support having a peripheral wall and an end wall (8) closing the peripheral wall transversely to the longitudinal geometric axis, and a measuring device disposed in an internal housing of the sensor support and for measuring a physical quantity in the cylinder body, wherein the measuring device comprises a sensor element sensitive to the physical quantity to be measured disposed against an inner surface of the end wall of the sensor support, and in which the wall of the end of the sensor support has a smaller thickness than the wall of the cylinder body (12).

Description

TECHNICAL FIELD The invention relates to the field of hydraulic control devices comprising a cylinder body provided with a bore defining a hydraulic chamber, in particular for controlling a clutch of a motor vehicle, and more particularly to measuring devices intended to measuring a physical quantity in the cylinder body of such a hydraulic control device.

Technological background

The use of a Hall effect magnetic sensor is known for measuring the axial position of a piston in the cylinder body of a hydraulic control device, for example in US-A-2005000772. In such a position measuring system, interference immunity and measurement accuracy are directly related to the gap distance between the sensor and the magnetic target. summary

Some aspects of the invention are based on the observation that high-quality physical measurements are made necessary, particularly in the automobile industry, by the development of sophisticated driving assistance functions and more generally by the progress of driving. automating.

An idea underlying the invention is to achieve the integration of a sensor assembly in a cylinder body in a manner that allows physical measurements of high quality, including electromagnetic measurements or pressure measurements or temperature, while offering a relatively simple and economical implementation.

For this, according to one embodiment, the invention provides a sensor assembly for a hydraulic control device comprising a cylinder body provided with a bore defining a hydraulic chamber, the sensor assembly being intended to be arranged in a through passage. formed in a wall of the cylinder body and opening into the hydraulic chamber, the sensor assembly comprising: a sensor support having a peripheral wall disposed around a longitudinal geometric axis of the sensor support and an end wall closing the wall peripheral device transverse to the longitudinal geometric axis, and a measuring device disposed in an internal housing of the sensor support and for measuring a physical quantity in the cylinder body, the inner housing being delimited by the peripheral wall and the wall of end of the sensor support, wherein the measuring device comprises an element A sensor responsive to the physical magnitude to be measured is disposed against an inner surface of the end wall of the sensor support, and wherein the end wall of the sensor support has a smaller thickness than the wall of the cylinder body. The invention also provides a hydraulic control device comprising a cylinder body provided with a bore defining a hydraulic chamber and a sensor assembly aforesaid arranged in a sealed manner in a through passage formed in a wall of the cylinder body and opening into the chamber in which a ratio between the thickness of the end wall of the sensor support and the thickness of the wall of the cylinder body is less than 100%, preferably less than 50%, more preferably less than 25% and even more preferably less than 20%.

Thanks to these characteristics, the distance separating the sensor element from the hydraulic chamber can be reduced to below the thickness of the wall of the cylinder body, which contributes to improving the accuracy of the measurements taken by the element. sensor.

According to advantageous embodiments, one or more of the following features may also be provided.

According to one embodiment, the sensor support has an outer shape of revolution around the longitudinal geometric axis. Thanks to such a geometry, the realization of a tight connection between the sensor support and the cylinder body is facilitated.

According to one embodiment, the sensor support has a generally cylindrical shape of revolution, with one or more stages of different diameters. The presence of several stages makes it possible in particular to define an axial abutment position of the sensor support against a suitable shoulder, which facilitates the positioning of the sensor assembly.

According to one embodiment, the sensor assembly further comprises a seal disposed around an outer surface of the peripheral wall to provide a sealed assembly with an inner surface of the through passage. According to one embodiment, the outer surface of the peripheral wall has a groove for receiving the seal, for example an O-ring.

Such a sensor assembly may be configured to perform different physical measurements in the cylinder body. According to one embodiment, the sensor element is sensitive to pressure, for example consisting of a piezoelectric sensor. According to another embodiment, the sensor element is sensitive to a magnetic field, for example consisting of a Hall effect sensor or other.

According to one embodiment, the measuring device is an electronic device comprising an integrated component (chip) encapsulated on interconnect tabs. This implementation is also known in the English terminology "lead-frame packaging". Thanks to this embodiment, the integration of the measuring device into the sensor support can be facilitated since a printed circuit board is not necessary and a greater miniaturization of the measuring device is thus obtained. .

According to one embodiment, the measuring device comprises an electrical connection element accessible from one side of the sensor support opposite to the end wall.

According to one embodiment, an outer surface of the end wall of the sensor support is arranged in alignment with an inner surface of the bore of the cylinder body. Thanks to these characteristics, the geometry of the hydraulic chamber is not disturbed by the sensor assembly, so that the operation of the hydraulic control device is not affected in an unpredictable manner.

According to one embodiment, the hydraulic control device further comprises a piston slidably mounted in the bore of the cylinder body to modify a volume of the hydraulic chamber and a magnet carried by the piston, and the sensor element is sensitive to the magnetic field of the magnet for measuring an axial position of the piston in the bore of the cylinder body.

According to one embodiment, the through passage receiving the sensor assembly is formed in a side wall of the cylinder body, preferably at an axial position which corresponds substantially to half the piston stroke between a rear rest position and a maximum advance position. Thanks to these characteristics, the distance between the magnet and the sensor element can be optimized for the entire operating range of the hydraulic control device.

According to one embodiment, the magnet carried by the piston is arranged in a peripheral zone of the piston, and the through passage receiving the sensor assembly is formed in a side wall of the cylinder body on the side of the peripheral zone of the piston comprising the magnet. Thanks to these characteristics, the distance between the magnet and the sensor element can be further reduced.

According to one embodiment, the cylinder body further comprises a fixing sleeve projecting from an outer surface of the wall of the cylinder body and extending the through passage formed in the wall of the cylinder body, the fixing sleeve having a end opening turned away from the cylinder body and in which the sensor assembly is engaged. The sensor assembly can be attached to the attachment socket in various ways. According to one embodiment, the fixing sleeve comprises means for attaching the sensor assembly to the cylinder body, for example at least one notch intersecting a lateral wall of the fixing sleeve transversely to an axis of the fixing sleeve, the sensor holder having a groove arranged in line with the notch, and a fastener, for example clip or key, is engaged together in the notch of the fixing sleeve and in the groove of the sensor holder for fixing the sensor assembly to the cylinder body.

According to another embodiment, the fixing sleeve and the sensor support are made of a heat-sealable synthetic material, and a sealed welded connection is made between the fixing sleeve and the sensor support all around the sensor support.

According to one embodiment, the cylinder body and the sensor support are made of synthetic materials, for example polyamides.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood, and other objects, details, features and advantages thereof will become more clearly apparent from the following description of several particular embodiments of the invention, given solely for the purposes of the invention. illustrative and not limiting, with reference to the accompanying drawings. - Figure 1 is an axial sectional view of a hydraulic control device for controlling a motor vehicle clutch, provided with a sensor assembly according to one embodiment of the invention. FIG. 2 is a view in axial section of the sensor assembly of FIG. 1. FIG. 3 is a partial view of a piston according to an alternative embodiment of a hydraulic sensor control device of FIG.

Detailed description of embodiments

There is shown in Figure 1 an embodiment of a transmitter cylinder 10, here for the control of a motor vehicle clutch. The transmitter cylinder 10 shown in Figure 1 corresponds to the configuration of the cylinder during delivery, that is to say, in particular before mounting on the vehicle for commissioning.

The emitter cylinder 10 comprises at least one generally tubular body 12 which extends axially along a main axis X of longitudinal orientation. The body 12 is made of at least two parts, respectively a front portion 12A and a rear portion 12B. The blind front portion 12A is defined axially at the front by a bottom 14 of transverse orientation while the rear portion 12B which is open axially towards the rear is likely to be closed by a cover 16 attached to fixing on the rear end of the body 12.

The body 12 of the cylinder 10 has an internal bore 18 in which a piston 20 slides axially, respectively forward or backward along the main axis X, between at least one extreme forward position, called actuation, and a extreme rear position, called rest. Advantageously, the piston 20 is made of plastic or thermoplastic material, preferably in a thermosetting material. The internal bore 18 of the emitter cylinder 10 defines, at the front, a hydraulic chamber 22 of variable volume which is delimited axially from front to back by the bottom 14 of the front portion 12A of the body 12 of the cylinder and by a part before 24, such as a front face, of the piston 20. The emitter cylinder 10 comprises sealing means which are interposed radially between the body 12 of the cylinder and the piston 20 and a control rod 28 which is connected in motion to the piston 20 by a hinge 30 of the ball joint type. The ball joint 30 is formed by cooperation of shapes between the front end of the control rod 28 which is adapted to cooperate with a complementary part of an insert 32 which is mounted in a recess 34 which is provided at the rear the piston 20.

The receiving cylinder (not shown) of a hydraulic clutch control device, generally of similar structure to the emitter cylinder 10 which has just been described, comprises a piston movable axially inside a body and delimiting a hydraulic chamber. variable volume pressure.

In operation, the transmitting cylinder 10 of a hydraulic clutch control device is intended to expel a fluid, such as oil, which is contained in the hydraulic chamber 22 into the receiving cylinder. The front portion 12A of the body comprises for this purpose a connector 38 which extends here parallel to the main axis X and which communicates at one end with the hydraulic chamber 22 via an orifice 40 which passes through the transverse bottom 14 of the body 12, and whose other end is able to allow the connection of a connecting pipe 42.

FIG. 1 shows the tip of the connecting pipe 42 engaged in connection 38 in which it is preferably held in position by locking means 44, such as a pin, alternatively by screwing. The other end of the conduit 42 is similarly connected to a connector of the receiving cylinder so that the respective hydraulic chambers of the transmitting cylinder 10 and the receiving cylinder are brought into communication.

Thus, when the clutch is engaged, the volume of the hydraulic chamber 22 of the emitter cylinder 10 is maximum while that of the control chamber of the slave cylinder is minimum. During a disengagement operation, the actuation of the control rod 28 of the piston 20 causes it to move axially forward, which causes the volume of the hydraulic chamber 22, the fluid of which is transferred via line 42, to be reduced towards the control chamber of the receiving cylinder whose volume increases in proportion.

The variation of the volume of the fluid of the control chamber of the receiving cylinder causes the displacement of the piston to act on disengaging means, usually a stop associated with at least one diaphragm that includes the clutch, either directly in the case of a hydraulic stop or indirectly via a rod acting on a fork and a mechanical stop. The emitter cylinder 10 may comprise piston return means, such as a spring, arranged in the hydraulic chamber and acting between the inner wall of the transverse bottom 14 and the front portion 24 of the piston 20.

Advantageously and as is illustrated in FIG. 1 for the emitter cylinder 10, such a spring can be omitted when the actuating means, such as the clutch pedal, not shown, already comprise return means capable of biasing the piston axially towards the rear by exerting a traction force on the control rod 28.

Thus, when the driver releases his action on the clutch pedal, the biasing means urge the piston 20 of the emitter cylinder 10 towards its rear extreme position of rest while, in the receiving cylinder, the return spring of the piston is again compressed by the diaphragm which urges axially backwards and thus brings the piston of the receiving cylinder to its initial rest position.

Preferably, the central part of the emitter cylinder 10, here formed by a stage 90 of larger diameter of the front portion 12A, comprises fixing means for fixing the emitter cylinder 10 on a fixed part of the vehicle, such as an apron . Such fixing means are for example constituted by a plate 50 provided with ears (not visible in Figure 1) which have holes for the passage of fasteners, such as screws.

The transmitter cylinder 10 further comprises another connector 52 arranged centrally and secured to the stage 90 of the body 12 intended to allow the connection of the hydraulic chamber 22 of the emitter cylinder 10 in particular to a not shown fluid replenishment tank. The connector 52 is here closed by a cap 53. In use, the refueling tank is generally mounted outside the transmitter cylinder 10 and is connected to the upper free end of the connector 52 by a pipe which takes the place of the cap 53..

The connector 52 comprises a channel 56 which passes through the lateral wall of the body 12 to open radially inwards in the central portion of the internal bore 18. The sealing of the hydraulic chamber 22 relative to the outside is ensured by sealing means which comprise at least one dynamic seal, here a front seal 58 of composite type which is associated with a cup 60 and a rear seal 62. Each seal 58 and 62 is mounted in a housing complementary to the body 12 forming a joint box and comprises a radial lip intended to cooperate with an outer cylindrical surface 64 of the piston 20.

In operation, the front seal 58 seals between the hydraulic chamber 22 and the feed channel 56 which opens axially between the seals 58 and 62, while the rear seal 62 seals between the piston 20 and the rear part. 12B behind channel 56.

However, if the rear seal 62 permanently seals regardless of the position of the piston 20 such is not the case of the front seal 58 which must allow the fluid supply of the chamber 22 through the channel 56 when the piston 20 in its extreme rear position of rest. The refeeding is carried out only when the piston 20 is in the extreme rear position of rest illustrated in FIG. 1 which is precisely determined by rear axial abutment means, such as a staple 68.

The piston 20 also comprises an elongated permanent magnet 25 which is housed in a blind hole 26 excavated axially from the front face 24, at a position offset laterally with respect to the main axis X, that is to say close to the side wall of the body 12 on one side of the body 12.

On the same side of the body 12, the front portion 12A has a fixing sleeve 11 which extends transversely to the axis X and which surrounds a passage 13 for receiving a magnetic sensor assembly 1 at a position as close as possible to the permanent magnet 25. The passage 13 opens into the hydraulic chamber 22 through an opening 15 formed in the side wall of the portion 12A of the body 12. Opposite the opening 15, the fixing sleeve 11 protrudes outside the body 12 and has an open end 17 through which the magnetic sensor assembly 1 can be inserted into the fixing sleeve 11.

FIG. 3 illustrates another arrangement of the permanent magnet 25 on the piston 20. The permanent magnet 25 is here an O-ring which is fixed on the front face 24 of the piston 20 by means of a flat-headed nail 29 of which the toothed rod 27 is engaged in a blind hole 27 of the piston 20. The magnetic sensor assembly 1 is shown in an external view in FIG. 1 and in section in FIG. 2. It consists essentially of a hollow support 2 and a a measuring device 3 housed in the hollow support 2. The hollow support 2 has a general shape of revolution.

As can be seen in FIG. 2, the hollow support 2 is similar to a cylindrical tube closed at one axial end by an end wall 4. The side wall 5 of the hollow support 2 has two successive stages of increasing diameter starting from the end wall 4. These two stages are separated by a conical shoulder 6 which abuts, in the assembled state shown in Figure 1, against a corresponding shoulder 19 inside the fixing sleeve 11, to define the maximum insertion position of the hollow support 2. In this assembled state, the outer surface 8 of the end wall 4 is in continuity with the internal surface of the bore 18.

In the smaller diameter stage of the hollow support 2, the side wall 5 has a first groove 21 in which is housed an O-ring 23 sealing the passage 13 once the magnetic sensor assembly 1 is mounted.

In the larger diameter stage of the hollow support 2, the side wall 5 has a second groove 31 for axially fixing the magnetic sensor assembly 1 in the attachment sleeve 11 by means of a fastener 33. More precisely, fastener 33 is an elastic ring or a U-shaped pin whose two branches engage in two diametrically opposed through-slots 49 of the fixing sleeve 11 and in the second groove 31 for locking the magnetic sensor assembly 1 in the fixing sleeve 11.

The hollow support 2 is made of synthetic material combining lightness and mechanical strength, for example polyamides. Alternatively, a diamagnetic material such as aluminum may be employed. As can be seen in FIG. 2, the end wall 4 is thinner than the side wall 5 and, in any case, much thinner than the side wall of the cylinder body 12 surrounding the bore 18. In addition, the device 3 located in the hollow support 2 comprises a magnetic sensor 45 placed against the inner surface of the end wall 4, so as to be as close as possible to the hydraulic chamber 22, namely separated from it essentially by the thickness of the end wall 4. The magnetic sensor assembly 1 and the permanent magnet 25 provide a system for measuring the position of the piston 20, the principle of which is known elsewhere. Thanks to the arrangement of the magnetic sensor 45, a particularly small gap can be obtained, which improves the accuracy of the measurements.

In an exemplary embodiment, the following dimensions may be adopted for the hollow support 2: outer diameter of between 10 and 12 mm, internal diameter of between 6 and 7 mm, thickness of the end wall 4 equal to 1 mm.

The outer portion of the magnetic sensor assembly 1 does not meet very strict dimensional requirements. In the embodiment of FIGS. 1 and 2, a cylindrical cover 47 extends the hollow support 2 and contains other electronic components for supplying and / or processing the signal. Finally, a connection cable 48 makes it possible to connect the magnetic sensor assembly 1 to the on-board information system of the vehicle.

The position measurements of the piston 20 of the transmitter cylinder 20 can be exploited by various driving assistance functions, for example the management of an automatic parking brake, the management of a cruise control, the management of a automatic engine start, etc.

In an alternative embodiment, the arrangement described above is used to place a piezoelectric pressure sensor in the immediate vicinity of the hydraulic chamber 22. According to one embodiment, several sensors of different types are placed in the hollow support 2. The use of the verb "to include", "to understand" or "to include" and its conjugated forms does not exclude the presence of other elements or steps other than those set out in a claim. The use of the indefinite article "a" or "an" for an element or a step does not exclude, unless otherwise stated, the presence of a plurality of such elements or steps.

In the claims, any reference sign in parentheses can not be interpreted as a limitation of the claim.

Claims (15)

A sensor assembly (1) for a hydraulic control device (10) having a cylinder body (12) having a bore (18) defining a hydraulic chamber (22), the sensor assembly being adapted to be arranged in a a through passage (15) formed in a wall of the cylinder body and opening into the hydraulic chamber, the sensor assembly comprising: a sensor support (2) having a peripheral wall (5) arranged around a longitudinal geometric axis of the sensor support and an end wall (4) closing the peripheral wall transversely to the longitudinal geometric axis, and a measuring device (3) disposed in an internal housing of the sensor support and for measuring a physical quantity in the cylinder body, the inner housing being delimited by the peripheral wall (5) and the end wall (4) of the sensor support, in which the measuring device (3) comprises an element sensor (45) responsive to the physical magnitude to be measured disposed against an inner surface of the end wall (4) of the sensor support, and wherein the end wall (4) of the sensor support has a thickness less than the wall of the cylinder body (12). 2. Sensor assembly according to claim 1, wherein the sensor support (2) has an outer shape of revolution about the longitudinal geometric axis. 3. Sensor assembly according to any one of claims 1 to 2, further comprising a seal (23) arranged all around an outer surface of the peripheral wall (5) to achieve a sealed assembly with an inner surface crossing. 4. Sensor assembly according to any one of claims 1 to 3, wherein the sensor element (45) is sensitive to pressure, for example consisting of a piezoelectric sensor. 5. sensor assembly according to any one of claims 1 to 3, wherein the sensor element (45) is sensitive to a magnetic field, for example consisting of a Hall effect sensor. 6. Sensor assembly according to any one of claims 1 to 5, wherein the measuring device (3) is an electronic device comprising an integrated component encapsulated on interconnect tabs. Sensor assembly according to any one of claims 1 to 6, wherein the measuring device comprises an electrical connection element (48) accessible from one side of the sensor support opposite to the end wall (4). 8. Hydraulic control device (10) comprising a cylinder body (12) provided with a bore (18) defining a hydraulic chamber (22) and a sensor assembly (1) according to any one of claims 1 to 7 arranged sealingly in a through passage (15) formed in a wall of the cylinder body (12) and opening into the hydraulic chamber (22), wherein a ratio of the thickness of the end wall (4) of the support sensor (2) and the wall thickness of the cylinder body (12) is less than 100%, preferably less than 50%, more preferably less than 25% and even more preferably less than 20% . 9. Device according to claim 8, wherein an outer surface (8) of the end wall (4) of the sensor support (2) is arranged in alignment with an inner surface of the bore (18). of the cylinder body. Apparatus according to any of claims 8 to 9, further comprising a piston (20) slidably mounted in the bore of the cylinder body for changing a volume of the hydraulic chamber (22) and a magnet (25). ) carried by the piston, wherein the sensor element (45) is sensitive to the magnetic field of the magnet for measuring an axial position of the piston (20) in the bore of the cylinder body (12). 11. Device according to claim 10, wherein the through passage (15) receiving the sensor assembly is formed in a side wall of the cylinder body, at an axial position which substantially corresponds to half the stroke of the piston (20). between a back rest position and a maximum feed position. 12. Device according to claim 10 or 11, wherein the magnet (25) carried by the piston (20) is arranged in a peripheral zone of the piston, and wherein the through passage (15) receiving the sensor assembly is provided in a side wall of the cylinder body (12) on the side of the peripheral zone of the piston comprising the magnet. Device according to any one of claims 8 to 12, wherein the cylinder body (12) further comprising a fixing sleeve (11) projecting from an outer surface of the wall of the cylinder body and extending the passage through (15) formed in the wall of the cylinder body, the fixing sleeve (11) having an end opening (17) facing away from the cylinder body and in which the sensor assembly (1) is engaged . 14. Device according to claim 13, wherein the fixing sleeve (11) comprises a notch (49) intersecting a lateral wall of the fixing sleeve transversely to an axis of the fixing sleeve, the sensor support having a groove ( 31) arranged in line with the notch (49), and in which a clip (33) is engaged together in the notch of the fixing sleeve and in the groove of the sensor support for fixing the sensor assembly (1). to the cylinder body (12). 15. Device according to any one of claims 13 to 14, wherein the fixing sleeve (11) and the sensor support (2) are made of a heat-sealable synthetic material, and wherein a sealed welded connection is made between the mounting sleeve and sensor bracket all around the sensor bracket.