Inductive position sensor with fluid circulation system

Abstract

The present invention relates to an inductive position sensor (1) for a rotating electric machine comprising a printed circuit board (12) on which at least one transmitting element (13) is arranged, wherein the transmitting element is intended to transmit an oscillating magnetic field towards a rotating target (2) in order to generate a modified oscillating magnetic field, and at least one receiving device (14) intended to detect the modified oscillating magnetic field, characterised in that it is configured to allow a fluid to flow into the inside of a rotor shaft (31) of the electric machine (3).

Description

[0001] Description

[0002] Title of the invention: Inductive position sensor with fluid circulation system

[0003] The present invention relates to the field of position sensors. And more particularly to an inductive position sensor comprising a fluid circulation system.

[0004] Inductive position sensors, known as eddy current sensors, use a magnetic field to determine the angular position of the rotating target which forms a coupling element.

[0005] These position sensors are used in particular in electric motors of electric or hybrid vehicles comprising a rotor rotating relative to a stator.

[0006] The angular position of the rotor is determined relative to the stator. The target is mounted at the end of a rotor shaft to modify a magnetic field transmitted by a transmitter. The target is centered relative to an axis of rotation of the rotor. The target comprises several blades that provide a repetitive and periodic magnetic field pattern relative to the rotor rotation axis.

[0007] The position sensor is mounted fixed relative to the stator, opposite the target and the rotor. The position sensor comprises a printed circuit board (PCB) comprising at least one transmission element intended to transmit an oscillating magnetic field towards the target, generating a modified oscillating magnetic field at a given frequency.

[0008] The printed circuit board includes a receiving device for detecting the modified oscillating magnetic field and transmitting it to a signal processing unit provided on the printed circuit board to deduce the angular position of the target. The sensor is closed by a cover, and can then be glued, soldered or clipped to the housing of a motor.

[0009] The disadvantage of these prior art sensors comes from the fact that they do not themselves allow the lubrication of the electric motor, but require an additional external device. The present invention therefore aims to overcome one of the disadvantages of those of the prior art by proposing a position sensor comprising a system for lubricating the electric motor.

[0010] For this purpose, the present invention proposes an inductive position sensor for a rotating electrical machine comprising a printed circuit board on which are arranged at least one transmitting element intended to transmit an oscillating magnetic field towards a rotating target to generate a modified oscillating magnetic field, and at least one receiving device intended to detect the modified oscillating magnetic field, the sensor being configured to allow the circulation of a fluid to the interior of a rotor shaft of the electrical machine.

[0011] According to one embodiment of the invention, the sensor comprises a first channel and a second channel, the first channel is configured to be in communication with a fluid reservoir and to bring the fluid towards the second channel which is formed from the lower part of the body of the sensor and is configured to open into a rotor shaft.

[0012] According to one embodiment of the invention, the first channel is formed in the body of the sensor or is an attached element which is connected to the body of the sensor by welding, gluing, clipping or any other holding method.

[0013] According to one embodiment of the invention, the first channel and the second channel are arranged coaxially to the axis of the rotor and perpendicular to the printed circuit board of the sensor.

[0014] According to one embodiment of the invention, the second channel is a channel open over at least part of its length, in the form of a groove in which the fluid circulates.

[0015] According to one embodiment of the invention, the second end of the first channel opens between the lower part of the sensor body and the target, allowing the fluid to flow by gravity to the second channel.

[0016] According to an alternative embodiment of the invention, the first channel extends to the second channel.

[0017] According to one embodiment of the invention, the extension of the first channel is formed in the lower wall of the sensor body.

[0018] According to one embodiment of the invention, the extension of the first channel is formed by an additional conduit allowing the connection between the first channel and the second channel. According to one embodiment of the invention, the sensor comprises fluid circulation means to allow the circulation of a fluid to the interior of a rotor shaft of the electrical machine via at least one channel.

[0019] These methods allow the fluid to be channeled and carried to the canal. This prevents the fluid from dispersing.

[0020] According to one embodiment of the invention, the inductive position sensor comprises a first channel opening between an internal surface of the housing and the target and a second channel formed from the internal surface of the housing.

[0021] According to one embodiment of the invention, the fluid circulation means are formed at an internal surface of the housing.

[0022] According to one embodiment of the invention, the fluid circulation means are formed by at least one area that is thinner than the rest of the surface of the housing.

[0023] This area helps channel the fluid and carry it to the canal. This prevents the fluid from dispersing.

[0024] According to one embodiment of the invention, the underthickness zone is arranged at the arrival of the first channel and the inlet of the second channel.

[0025] According to one embodiment of the invention, the dimensions of the underthickness zone are calculated to optimize the channeling of the fluid.

[0026] According to one embodiment of the invention, the underthickness zone forms a hollow whose depth is between 0.1 mm and 3 mm.

[0027] According to one embodiment of the invention, the fluid circulation means also comprise at least one groove formed at an internal surface of the housing and opening into a thinner zone.

[0028] The presence of at least one groove makes it possible to channel the fluid and lead it via the groove to the underthickness zone and thus to the channel.

[0029] According to one embodiment of the invention, the fluid circulation means also comprise a rim arranged at the edge of the zone, opposite that where at least one groove opens.

[0030] Thus the fluid which arrives in the underthickness zone via the groove and the first channel, is contained in the zone thanks to the rim or wall and evacuated towards the second channel. The invention also relates to an electrical machine comprising a sensor according to the invention.

[0031] Other aims, characteristics and advantages of the invention will be better understood and will appear more clearly on reading the description given below, with reference to the appended figures, given by way of example and in which:

[0032] - [Fig. 1] is a representation of the sensor according to the invention according to a first face fixed on the electrical machine,

[0033] - [Fig. 2] is a representation of the sensor according to the invention on a second face,

[0034] - [Fig. 3] is a representation of the sensor according to the invention with the target,

[0035] - [Fig. 4] is a schematic representation of a longitudinal sectional view of the electrical machine with the sensor according to one embodiment of the invention a), according to another embodiment b),

[0036] - [Fig. 5] is a representation of the sensor according to the invention with a cap,

[0037] - [Fig. 6] is a longitudinal sectional representation of the sensor according to a first variant of the invention,

[0038] - [Fig. 7] is a representation of the sensor seen from above according to a first variant of the invention,

[0039] - [Fig. 8] is a longitudinal sectional representation of the sensor according to a second variant of the invention,

[0040] - [Fig. 9] is a representation of a detail of the sensor according to a second variant of the invention,

[0041] - [Fig. 10] is a representation of a detail of the sensor according to a second variant of the invention,

[0042] - [Fig. 11] is a longitudinal sectional representation of the sensor according to a second embodiment of the second variant of the invention,

[0043] - [Fig. 12] is a representation of a detail of the sensor according to one embodiment of the invention,

[0044] - [Fig. 13] is a schematic representation of the sensor according to an embodiment of the invention with different under-thickness zones.

[0045] The invention relates to an inductive position sensor 1, as illustrated in [Fig.l] to [Fig.3] integrating a lubrication system of an electric machine. The inductive position sensor 1 uses a magnetic field to determine the angular position of a visible rotating target 2 [Fig.2] which is used as a coupling element. The inductive position sensor 1 and the target are intended to be mounted in a rotating electric machine 3 illustrated [Fig.4] a and b such as an electric motor of an electric or hybrid vehicle comprising a rotor 32 rotating relative to a stator 33. The angular position of the rotor 32 is determined relative to the stator 33.

[0046] According to one embodiment of the invention, the sensor is fixed to the cover of the electrical machine by a screw-type fixing system 19.

[0047] As illustrated [Fig.4] a and b, the target 2 is mounted on one end of a shaft 31 of the rotor 32 to modify a magnetic field emitted by a transmitter.

[0048] According to one embodiment of the invention, the target 2 comprises an axis of rotation X which is aligned with an axis of rotation of the rotor 32. The target 2 comprises several blades 21 which provide a repetitive and periodic magnetic field pattern with respect to the axis of rotation of the rotor.

[0049] According to one embodiment of the invention, the sensor 1 is arranged opposite the target 2 at the end of the shaft 31 of the rotor. More precisely, the position sensor 1 is mounted fixed relative to the stator 33, opposite the target 2 at the end of the shaft 31 of the rotor. There is therefore, in order of positioning on the shaft, the rotor / stator 32, 33, then the target 2, then the position sensor 1. These elements are arranged coaxially with the axis X of the rotor shaft.

[0050] According to one embodiment of the invention, the sensor 1 is through-sensor, i.e. the shaft 31 of the rotor passes through the center of the sensor [Fig. 4a],

[0051] According to one embodiment of the invention, the sensor 1 is non-through, that is to say it is arranged at the end of the shaft 31 of the rotor [Fig. 4b],

[0052] The inductive position sensor 1 comprises at least one printed circuit board 12 (PCB) comprising at least one emission element 13 intended to emit an oscillating magnetic field towards the target 2, which returns a modified oscillating magnetic field at a given frequency.

[0053] This printed circuit board 12 comprises a receiving device 14 intended to detect the modified oscillating magnetic field and to transmit it to a signal processing unit 6 to measure the angular position of the target 2. The modified oscillating magnetic field generates an electromotive force at a given frequency in the receiving device 14. This electromotive force is processed by the signal processing unit 6 so as to provide output signals allowing the measurement of the position of the target 2. The inductive position sensor 1 is mounted fixed relative to the stator 33. The transmitting element 13 and the receiving device 14 of the inductive position sensor 1 are positioned opposite the target 2.

[0054] According to one embodiment of the invention, the receiving device 14 comprises several windings and has a circular section and more precisely an annular shape.

[0055] According to one embodiment of the invention, the number of windings of the receiving device 14 is proportional to the number of blades 21 (or angular sectors) of the target 2. According to one embodiment of the invention, the target 2 comprises at least two angular sectors 21, and for example 3, 4, 5 or 6.

[0056] The printed circuit board 12, the transmitting elements 13 and the receiving device 14 are housed in at least one housing 10 and supported by a base of the housing 10. This housing forms the body 10 of the sensor 1.

[0057] According to one embodiment of the invention, the signal processing unit 6 is positioned on the same substrate as the transmission and reception elements or on another substrate, housed in the housing.

[0058] According to one embodiment of the invention, the housing 10 is closed by a cover 11. In the context of the invention, the sensor 1 is configured to allow the circulation of a fluid to the interior of the shaft 31 of the rotor 32.

[0059] For this purpose, the sensor 1 comprises a first fluid inlet channel 16. This channel 16 is configured to be in communication with a fluid reservoir 4.

[0060] According to one embodiment of the invention, this first channel 16 is formed in the body 10 of the sensor 1. In this case, the sensor 1 comprises a plug 15 to close the opening made in the body of the sensor 1 during the creation of the first channel [Fig. 5],

[0061] According to one embodiment of the invention, the first channel 16 is an attached element which is connected to the body of the sensor by welding, gluing, clipping or any other holding method.

[0062] According to one embodiment of the invention, the first channel 16 is arranged coaxially to the axis X of the rotor and perpendicular to the card 12 of the printed circuit of the sensor 1. According to one embodiment of the invention [Fig. 6], the first channel 16 emerges from the body of the sensor 1 through an opening, of its first end 165, which is configured to be positioned at the level of a fluid reservoir 4, so as to receive the fluid from the reservoir by gravity.

[0063] According to one embodiment of the invention, the sensor 1 comprises a second channel 17 formed from the lower part of the body of the sensor 1. The lower part is that on which the printed circuit board rests, as opposed to the upper part which is open and on which the cover is positioned. More precisely, the second channel is formed from the internal face 101 of the housing 10, oriented towards the machine 3.

[0064] According to one embodiment of the invention, the second channel 17 is overmolded or molded with the housing 10.

[0065] According to one embodiment of the invention, the second channel 17 is arranged parallel to the axis X of the rotor and therefore parallel to the first channel 16.

[0066] According to a second variant of the invention, the first channel 16 extends to the second channel 17.

[0067] According to one embodiment of the invention, the second channel 17 is a channel open over at least part of its length, in the form of a groove. That is to say, it forms a U, or any other equivalent shape, in which the fluid circulates [Fig.9],

[0068] According to one embodiment of the invention, the longitudinal opening of the channel is oriented towards the first channel.

[0069] According to one embodiment of the invention, the second channel 17 is configured to open into the shaft 31 of the rotor 32. The shaft 31 of the rotor 32 has openings 34 allowing the fluid circulating in the second channel 17 to be distributed in the electrical machine 3 through the center of the axis X of the rotor shaft thanks to the centrifugal force which propels the fluid against the walls of the shaft. Thus, this configuration makes it possible to avoid the dispersion of the fluid directly at the outlet of the reservoir. With the configuration of the invention, the fluid is brought to the center of the rotor shaft and then dispersed through the interior of the rotor, which allows for better lubrication.

[0070] According to a first embodiment of the invention, the second end 166 of the first channel 16 opens between the lower part of the body 10 of the sensor and the target 2. The fluid can thus flow by gravity from the first channel 16, to a second channel 17, circulating between the lower part of the body of the sensor and the target. According to one embodiment of the invention, the second end 166 of the first channel 16 is sufficiently close to the lower wall of the body of the sensor 1 so that the fluid flows along this wall without being expelled throughout the compartment by the rotating target 2.

[0071] According to one embodiment of the invention, the fluid passes around the target through the channel, so that the fluid flow in the first channel is not disturbed by the rotational speed of the target.

[0072] An advantage of this variant is that the distance between the target and the printed circuit board is reduced and is completely circular. This allows for a completely cylindrical antenna, which allows for good signal accuracy even in the case of target flutter phenomena.

[0073] According to a second variant of the invention, the first channel extends to the second channel.

[0074] According to a first embodiment of this second variant [Fig. 8], the extension 162 of the first channel is formed in the lower wall of the sensor body. More precisely, the extension 162 of the first channel is formed in the thickness of the lower wall of the sensor body.

[0075] An advantage of this embodiment of this variant comes from the fact that the distance between the target and the printed circuit board is reduced. This is one of the important criteria for signal accuracy.

[0076] According to one embodiment of the invention, the extension 162 of the first channel 16 forms a protrusion 161 at the opposite surface of the visible printed circuit board [Fig. 7] and the interior 164 of the extension 162 of the first channel 16 is visible [Fig. 10]. According to one embodiment of the invention, the connection between the first channel 16 and the extension 162 of the first channel is made with an additional part 168 visible [Fig. 9] allowing the entry of the fluid 163 into the extension.

[0077] According to an embodiment of this second variant, the extension 162 of the first channel is formed by an additional conduit arranged in the thickness of the body 10 of the sensor 1.

[0078] According to one embodiment of the invention, the extension 162 of the first channel 16 opens into the second channel 17. According to a second embodiment of this second variant, the extension 162 of the first channel is formed by an additional conduit 18 [Fig. II]. This additional conduit 18 allows the connection between the first channel 16 and the second channel 17.

[0079] According to one embodiment of the invention, the additional conduit 18 is arranged between the body 10 of the sensor 1 and the target 2.

[0080] This allows for a completely cylindrical antenna 13, 14, which allows for maintaining good signal accuracy even in the case where there are target flapping phenomena.

[0081] In the context of the invention, the internal surface 101 of the housing 10 comprises visible means 180 for circulating the fluid [Fig. 12],

[0082] According to one embodiment of the invention, the fluid circulation means 180 are formed by at least one zone 181 of reduced thickness, relative to the rest of the surface of the housing, arranged at the level of the arrival of the first channel 16 of the fluid circulation means 180 and the inlet of the second channel 17. More precisely, the internal surface 101 of the housing 10 comprises a zone 181 forming a hollow between the arrival of the first channel 16 and the inlet of the second channel 17.

[0083] According to one embodiment of the invention, the dimensions of the underthickness zone 181 are calculated to optimize the channeling of the fluid. [Fig. 13]a), b) and c) illustrate different dimensions of the underthickness zone 181.

[0084] According to one embodiment of the invention, the underthickness zone 181 forms a hollow whose depth is between 0.1 and 3 mm, and for example 0.5 mm.

[0085] This zone allows the fluid to be channeled and conducted from the first channel 16 to the second channel 17. This prevents the fluid from dispersing, visible [Fig. 13]. In the context of the invention, the fluid circulation means 180 also comprise at least one groove 182 formed at the internal surface 101 of the housing. This groove has the shape of an incomplete circle and opens into the zone 181 in the lower thickness. According to one embodiment of the invention, the sensor comprises at least 2 grooves 182 and for example 3 grooves 182.

[0086] According to one embodiment of the invention, the grooves are spaced apart from each other. According to one embodiment of the invention, the grooves are arranged in spirals.

[0087] When the target 2 rotates, the direction C of rotation is indicated by the arrow in [Fig. 13], at least a portion of the fluid arriving from the conduit 16 is dispersed in the area between the target and the internal surface of the housing. The presence of at least one groove makes it possible to channel, arrow F, the fluid and to conduct it via the groove towards the underthickness area and thus towards the second channel 17.

[0088] In the context of the invention, according to one embodiment of the invention, the means 180 for circulating the fluid also comprise a rim 183 arranged at the edge of the zone, opposite that where at least one groove 182 opens.

[0089] According to one embodiment of the invention, the rim forms a wall whose height is between 0.1 and 3 mm, and for example 0.5 mm.

[0090] Thus the fluid which arrives in zone 181 in underthickness via the groove and the first channel

[0091] 16, is contained in zone 181 thanks to the edge or wall and evacuated towards the second channel

[0092] 17.

[0093] An advantage of these 180 fluid circulation means comes from the fact that they allow for a reduced distance between the target and the printed circuit board, which is one of the important criteria for signal accuracy. These means also allow for a completely cylindrical antenna 13, 14, which allows for good signal accuracy to be maintained even in the case where there are target flapping phenomena.

[0094] According to one embodiment of the invention, the fluid is oil, and more precisely lubricating oil. The circulation of the oil via the shaft allows the lubrication of the electric machine 3, and more precisely of the pinions 5 of the electric machine 3.

[0095] Thus, such a sensor according to the invention allows the lubrication of the elements of the electrical machine without an additional system.

[0096] The invention also relates to an electrical machine 3 comprising a sensor 1 as described previously, according to the two variants.

[0097] The scope of the present invention is not limited to the details given above and allows embodiments in many other specific forms without departing from the scope of the invention. Therefore, the present embodiments should be considered by way of illustration, and may be modified without departing from the scope defined by the claims.

Claims

CLAIMS 1. Inductive position sensor (1) for a rotating electrical machine comprising a printed circuit board (12) on which are arranged at least one transmitting element (13) intended to transmit an oscillating magnetic field towards a rotating target (2) to generate a modified oscillating magnetic field, and at least one receiving device (14) intended to detect the modified oscillating magnetic field, characterized in that it is configured to allow the circulation of a fluid to the interior of a rotor shaft (31) of the electrical machine (3).

2. Inductive position sensor (1) according to claim 1, comprising a first (16) channel and a second (17) channel, the first (16) channel is configured to be in communication with a fluid reservoir (4) and to bring the fluid towards the second channel (17) which is formed from the lower part of the body of the sensor and is configured to open into a rotor shaft (31).

3. An inductive position sensor (1) according to claim 1 or 2, wherein the first channel (16) is formed in the sensor body or is an insert which is bonded to the sensor body by welding, gluing, clipping or any other holding method.

4. Inductive position sensor (1) according to one of claims 1 to 3, wherein the first channel (16) and the second channel (17) are arranged parallel to the axis (X) of the rotor and perpendicular to the printed circuit board (12) of the sensor.

5. Inductive position sensor (1) according to one of claims 1 to 4, in which the second channel (17) is a channel open over at least part of its length, in the form of a groove in which the fluid circulates.

6. Inductive position sensor (1) according to one of claims 1 to 5, wherein the second end (165) of the first channel opens between the lower part of the body of the sensor and the target (2), allowing the fluid to flow by gravity to the second channel (17).

7. Inductive position sensor (1) according to one of claims 1 to 5, wherein the first channel (16) extends to the second channel (17).

8. Inductive position sensor (1) according to claim 7, wherein the extension (162) of the first channel (16) is formed in the lower wall of the sensor body.

9. Inductive position sensor (1) according to claim 7, wherein the extension (162) of the first channel is formed by an additional conduit (18) allowing the connection between the first channel and the second channel.

10. Electrical machine comprising a sensor according to one of claims 1 to 9.

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