TECHNICAL FIELD OF THE INVENTION

This invention relates to a detection assembly for a pin to be used in a joint between two parts that can pivot one with respect to the other. The invention also relates to a pin for such a joint and to an instrumented joint system between a first part and a second part that can pivot one with respect to the other and to an automotive vehicle equipped with such an instrumented joint system. Finally, the invention relates to a process for manufacturing a detection assembly for pin of a joint between two pivoting parts.

BACKGROUND OF THE INVENTION

Instrumented joint systems are used, for example on the articulated arms of an earth moving machine, in order to control the angular movement of one part with respect to another. Such joint systems may include a pin fixed with respect to one part and mounted with a possibility of rotation with respect to another part of the joint. It is known from FR-A-2 904 671 to incorporate, within such a pin, an assembly for detecting some parameters of the rotation of one of the articulated parts with respect to the other. This detection assembly includes two magnetically cooperating components, one of them being fastened with the pin, wherein the other one is rotating with respect to the pin. A ball bearing is used to allow the rotation of one of these components with respect to the pin. This detection assembly is made of several parts which must be installed one after the other within the housing, which requires high technical skills and is time consuming. Moreover, the diameter of this assembly is quite important with respect to the diameter of the pin, which can generate weak zones in the pin, with a risk of breakage in use of the joint. SUMMARY OF THE INVENTION

The invention aims at solving these problems with a new detection assembly for pin of a joint whose resistance and lifetime can be improved and which is easier, faster and more economical to incorporate into a pin. The invention concerns a detection assembly for a pin of a joint between two parts that can pivot one with respect to the other, around a central longitudinal axis of the pin, the assembly being adapted to detect at least one rotation parameter of one of the parts with respect to the other part, to be mounted inside a housing of the pin and including at least one rolling bearing and first and second magnetically cooperating components, whereas a first one of these components is supported by a printed circuit board. This detection assembly is characterized

• in that it includes:

- a support member fast in rotation with the pin, a first ring of the first rolling bearing being mounted on the support member whereas the support member holds a first one of the magnetically cooperating components

- a tubular body

• in that the printed circuit board includes at least two rigid parts joined by a flexible hinge with flexible connectors and

• in that the printed circuit board is at least partially located in the internal volume of the tubular body.

Thanks to the invention, the printed circuit board can be folded in order to have relatively small transverse dimensions, so that the tubular body can be of a relatively small diameter. The structure of the detection assembly can be very compact in diameter, so that the diameter of the housing can be small on most of its length. Therefore the pin is not embrittled by this housing.

A rotation parameter of one part with respect to the other is a parameter which is representative of the pivoting movement of one part with respect to the other. Such a parameter can be an angle measuring the angular position of one part with respect to the other, around the central axis of the pin. Such a parameter can also be speed, displacement, acceleration or vibration.

According to further aspects of the invention, which are advantageous but not compulsory, the detection assembly might incorporate one or several of the following features: - The printed circuit board includes three rigid parts and two flexible hinges, namely a first rigid part supporting the first component, a second rigid part and a third rigid part, a first flexible hinge joining the first rigid part to the second rigid part and a second flexible hinge joining the second rigid part to the third rigid part. - The tubular body is provided with means for holding at least one of the rigid parts of the printed circuit board in position within its internal volume.

- A peripheral edge of the at least one rigid part is at least partially received within an internal groove of the tubular body.

- A tapered surface of the tubular body converges towards the groove. - At least one clearance is provided between the peripheral edge of the at least one rigid part and a radial inner surface of the tubular body.

- The internal volume of the tubular body is at least partially filled with a protective material which surrounds the printed circuit board.

- The protective material goes from one side of the at least one rigid part to the other side, through the at least one clearance.

The invention also concerns a pin for a joint between two parts that can pivot one with respect to the other around a longitudinal axis of the pin, this pin including a detection assembly as mentioned here-above.

According to further aspects of the invention, which are advantageous but not compulsory, the pin might incorporate one or several of the following features:

- The first rigid part is perpendicular to the central longitudinal axis of the pin, whereas the second and third rigid parts are parallel to the central longitudinal axis when the detection assembly is mounted in the housing.

- A second ring of the first rolling bearing is mounted at a first end of the tubular body, whereas the detection assembly includes a second bearing, with a first ring mounted on the tubular body at the second end of the tubular body, and a nut provided with an external thread cooperating with an internal thread of the housing, the nut being adapted to exert on the second rolling bearing an axial effort directed towards the first end of the tubular body, this axial effort pressing a surface of the support member against a corresponding surface of the housing.

When the support member or the body is mounted on a ring of a bearing or when a ring of a bearing is mounted on the support member or the body, these elements are fixed in rotation with each other. The invention also concerns an instrumented joint system between a first part and a second part that can pivot, around a central geometrical axis of the joint, one with respect to the other. This system has a pin as mentioned here-above, whose central longitudinal axis is aligned on the central geometrical axis of the joint, whereas the pin is fastened with the first part and mounted with respect to the second part with a possibility of rotation. Such an instrumented joint system is more economic and more reliable than the ones of the prior art.

The invention also concerns an automotive vehicle, in particular a construction vehicle, an agricultural vehicle or a mining vehicle, equipped with an instrumented joint system as mentioned here-above. Such a vehicle is more economic and more reliable than the ones of the prior art.

Finally, the invention relates to a process for manufacturing a detection assembly as mentioned here-above and, more specifically, to a process for manufacturing a detection assembly for a pin of a joint between two parts that can pivot one with respect to the other around the central longitudinal axis of the pin, the assembly beδng adapted to detect at least one rotation parameter of one of the parts with respect to the other part, thanks to a first and a second magnetically cooperating components, one of which is supported by a printed circuit board. This process is characterized in that it includes at least the following steps: a) building the printed circuit board with at least two rigid parts and one flexible hinge with flexible connectors, b) folding the printed circuit board at the level of the hinge, so that at least one dimension of the printed circuit board is reduced, c) introducing the folded printed circuit board within a tubular body, d) mounting a first end of the tubular body on a ring of a rolling bearing, e) mounting a support member which holds the component which is not supported by the printed circuit board on the other ring of the rolling bearing, and f) installing and locking in position the tubular body, the rolling bearing and the support member in a housing of the pin.

In the process mentioned here-above, the order of some of the steps can be inverted. According to a first advantageous but non compulsory aspect of the invention, the process includes, between steps c) and d): g) filling at least partially the internal volume of the tubular body with a protective material which surrounds the printed circuit board. According to another advantageous but not compulsory aspect of the invention, the process includes at least the following further steps, prior to step f): h) mounting a second end of the tubular body on a ring of a second rolling bearing, i) mounting a threaded nut with respect to the second rolling bearing in a position such that the threaded nut can exert on the second rolling bearing an axial effort directed towards the first end of the tubular body.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood on the basis of the following description which is given in correspondence with the annexed figures and as an illustrative example, without restricting the object of the invention. In the annexed figures:

- Figure 1 is a cross-view in axial section of an instrumented joint system according to the invention, including a detection assembly and a pin according to the invention

- Figure 2 is a perspective view of a pin of the invention used in the joint system of figure 1 , together with a connecting rod;

- Figure 3 is a cut view in plane III on figure 2;

- Figure 4 is an enlarged view of detail IV on figure 3; - Figure 5 is a view similar to figure 4 when a detection assembly is being mounted on the pin of figures 2 to 4;

- Figure 6 is a perspective exploded view of a detection assembly belonging to the pin of figures 2 to 5;

- Figures 7 to 10 are perspective views representing the forming process of a printed circuit board belonging to the pin;

- Figure 11 is a view of the printed circuit board in the configuration of figure 10, viewed from another angle; - Figure 12 is a longitudinal cut view of the detection assembly during a first step of its manufacturing process;

- Figure 13 is a longitudinal cut view along line XIII-XIII on figure 12, line XII- XII shows the cut line used for figure 12; - Figure 14 is a partial longitudinal cut view of the detection assembly during a further manufacturing step, this figure being taken in the same plane as figure 12, and

- Figure 15 is a cut view, in the same plane as figure 13, of the detecting assembly during a further manufacturing step.

DETAILED DESCRIPTION OF SOME EMBODIMENTS The instrumented joint system 10 represented on figure 1 connects a first part 12 to a second part 14 of an earth moving machine. Part 12 is, for example, an articulated arm of a backhoe loader which is supposed to move with respect to part 14 fixed and secured to a non represented chassis of the machine.

Part 14 includes two beams 16 and 18 connected by a spacer 20. One plain bearing or bushing 22 or 24 is mounted at one extremity of each beam 16 or 18 and dimensioned to receive each a pin 30 or 32 with a possibility of rotation around a common axis Xio, which is an axis of rotation of parts 12 and 14, one with respect to the other.

Each pin 30 or 32 is cylindrical, with a circular basis. X ₃ o and X32 respectively denote the central longitudinal axes of pins 30 and 32. In the assembled configuration of joint system 10, axes X30 and X32 are aligned on axis X10.

Part 12 has globally the shape of a U, with both ends of its branches forming a clevis 34 or 36 surrounding the ends of the beams 16 and 18 and plain bearings

22 and 24. Pin 30 is fixedly mounted within two housings 34A and 34B of clevis 34 which are aligned along axis X10. Pin 30 is immobilized in rotation around axes X30 and X ₁₀ with respect to part 12 thanks to a locking gudgeon 38. Similarly, pin 32 is held in position with respect to two aligned housings 36A and 36B of clevis 36 thanks to a locking gudgeon 40.

In order to detect the angular displacement of moving part 12 relative to fixed part 14, the joint system 10 also includes a detection assembly 50 which detects a rotation angle between parts 12 and 14 and is mounted within one housing 52 drilled in pin 30 and centered on axis X30.

A connecting bar 54 is connected by two bolts 56 to beam 16. This connecting bar is also connected by three bolts 58 to a socket 60 belonging to assembly 50. Bolts 58 are represented by their respective longitudinal axes on figures 2 to 4.

Assembly 50 includes a support member 64 provided with a taper shank 66 whose external surface 68 is frustroconical and centered on axis X30 when assembly 50 is mounted within housing 52. The geometry of taper shank 66 corresponds to the geometry of an end portion 70 of housing 52 whose peripheral surface 72 is also frustroconical. Angle α denotes the semitop angle of surface 68, whereas angle β denotes the semitop angle of surface 72. Angles α and β have the same value, so that support member 64 can be blocked in rotation by adherence around axis X30, with respect to pin 30, when surfaces 68 and 72 are being pressed one against the other.

Support member 64 also includes a cylindrical base part 73 provided with a central recess 74 for receiving a magnetized ring 76 which is blocked within recess 74 by cooperation of shapes. Magnetized ring is actually made of a magnet.

Assembly 50 also includes a first ball bearing 80 whose internal and external rings are respectively denoted 82 and 84. 86 denotes the balls of bearing 80.

In this description, the expression "rolling bearing" is meant to cover any type of bearing having rolling parts, e.g. balls, needles or rollers. A ball bearing is an example of a rolling bearing.

Internal ring 82 of ball bearing 80 is fixedly mounted on cylindrical base part 73.

Assembly 50 also includes a tubular body 90 in a form of a sleeve, with a first end 91 surrounding ball bearing 80. Actually, external ring 84 is fixedly mounted within first end 91.

92 denotes the second end of body 90, that is the end opposite to first end 91.

Assembly 60 also includes a second ball bearing 100 whose internal and external rings are respectively denoted 102 and 104, whereas its balls are denoted 106. Ring 102 is fixedly mounted on end 92 of body 90. Ring 102 is also fixedly mounted on socket 60, so that items 60 and 90 are fast in rotation with each other, through ring 102.

A nut 110 is located around bearing 100 and provided with an external thread 112 adapted to cooperate with an internal thread 114 of housing 52. Nut 110 is provided with a flange 116 extending radially towards axis X30. Ring 104 is fixedly mounted within nut 110. The mutual locking of the nut 110 and the housing 52 by means of mutually engaging threads makes it possible to easily remove the nut in case for instance of maintenance or inspection. However, and alternatively, the nut could be locked into the housing by other means such as gluing or force-fitting.

An elastically deformable washer 120 is located axially between flange 116 and ball bearing 100.

As shown on figure 4, an axial effort E, that is an effort parallel to axis X30, can be exerted by flange 116 on washer 120, this effort E being transmitted to ball bearing 100 by washer 120. Effort E is then transmitted to body through bearing

100 and, from body 90 to support member 64 via ball bearing 80. Therefore, effort

E, which is exerted by nut 110 on ball bearing 100 via washer 120, firmly presses surface 68 against surface 72, thus ensuring an immobilization in rotation of member 64 with respect to pin 30, thanks to the cooperation of shapes and adherence between surfaces 68 and 72.

A magnetic sensor 130, e.g. in the form of a hall effect cell, is installed in the interior volume 132 of tubular body 90, at an axial distance di of magnetized ring 76 sufficiently small to allow sensor 30 to detect a rotation of ring 76 with respect to body 90. Elements 64 and 76 are fixed in rotation with respect to pin 30, thanks to effort E. Elements 90 and 60 can rotate with respect to pin 30 when part 14 moves with respect to part 12, thus driving connecting rod 54 and socket 60 in rotation around axis X30.

Sensor 130 is mounted on a printed circuit board 140 (PCB) which is made of three rigid plates of insulating material 142, 144 and 146 connected by two hinges

148 and 150 including flexible conductors. On the figures, the electronic components of the circuit supported by printed circuit board 140 are not represented, but for sensor 130. In the sense of this description, plates 142, 144 and 146 are rigid insofar as they are not supposed to be folded or bended. These plates can be made of any suitable electrically insulating material, e.g. from a synthetic resin such as polyamide or epoxy.

In the configuration of figure 7, plates 142, 144 and 146 extend in the same plane and hinges 148 and 150 are planar. PCB 140 has a width whose value wi corresponds to the cumulated widths of plates 144 and 146 and of hinge 150. Its length has a value h which corresponds to the sum of the lengths of plates 142 and 144 and the length of hinge 148.

In order for PCB 140 to fit into the interior volume 132 of body 90, PCB 140 is folded along hinge 148 by pressing plate 146 against plate 144, as represented by arrow Ai on figure 8. This enables to reach the configuration of figure 9 where the width of PCB 140 has been decreased to a value W ₂ which is about 50% of value wi. It is then possible to fold hinge 148, as shown by arrow A ₂ . One reaches the configuration of figure 9 where plate 142 is perpendicular to plates 144 and 146 and the value I ₂ Of the length of PBC 140 is smaller than h.

As clearly visible on figure 11 , plate 142 is provided with two openings 152 and 154 substantially diametrically opposed. Apart from these openings, plate 142 has substantially the shape of a disk.

Once it has the configuration of figures 10 and 11 , PCB 140 can be introduced within tubular body 90 via its first end 91 , in such a way that plates 144 and 146 penetrate within volume 132 in order to protrude from end 92, whereas the edge 156 of plate 142 is introduced within an internal groove 158 of body 90.

The introduction of PBC 140 within body 90 is represented by arrow A ₃ on figures 12 and 13. X90 denotes the central longitudinal axis of body 90. This axis is aligned with axis X30 when assembly 50 is mounted within housing 52.

Once its edge 156 is received in groove 158, plate 142 is held in position within the internal volume 132 of body 90, which determines the position of PCB 140 along axis X90. In this position, PCB 140 is also partly engaged within the internal volume 62 of socket 60.

Between end 91 and groove 158, body 90 is provided with a frustroconical internal surface 160, which allows to guide plate 142 towards groove 158 when pushing PCB 140 in the direction of second end 92. Close to their respective ends opposite hinge 148, rigid plates 144 and 146 are respectively provided with connectors 164 and 166 adapted to receive the respective ends of electric conductors 168 which belong to a cable 170 connected to a plug 172 by which assembly 50 can be connected to a non represented electronic control unit (ECU). Connectors 164 and 166 are located within volume 62 when PCB 140 is installed within body 90. The fact that cable 170 is flexible and that socket 60 is located outside housing 52 facilitates connection of assembly 50 to the ECU.

Plates 144 and 146 are parallel to axis X90 when PCB 140 is installed within body 90, whereas plate 142 is perpendicular to this axis, thus allowing to locate sensor 130 in front of magnetized ring 76, at distance di .

In this configuration, and in order to protect PCB 140 from pollution and/or contact with external elements, a potting 180 of insulating synthetic resin is molded within the internal volumes 62 and 132. This potting 180 also permits to hold PCB 140 in position within volumes 62 and 132.

As shown on figures 14 and 15, potting 180 extends on both sides of plate 142. Potting 180 is flush with the surface 134 of sensor 130 oriented towards ring 76 when elements 64 and 80 are mounted on body 90. The presence of potting 180 on both sides of plate 142 is possible thanks to the openings 152 and 154. In other words, even if the edge 156 of plate 142 is in position within groove 158, potting 180 can flow on both sides of plate 142 since plate 142 does not extend up to groove 158 at the level of openings 152 and 154.

Once a sub-assembly made of items 60, 90, 100, 110, 130, 140, 170, 172 and 180 has been realized, as shown on figure 14, it is possible to mount within end 91 of tubular body 90 items 64 and 80, in order to reach the configuration of figure 15. In this configuration, assembly 50 constitutes a unitary item which can be easily manipulated in order to be installed within housing 52, without specific skills and in a relatively short time.

With this respect, socket 60 is provided with an external flange 182 which protrudes radially in such a way that it prevents nut 110 from falling out of assembly 50 in the direction of arrow A ₄ on figure 15.

Once assembly 50 has been constituted as explained here-above, it can be introduced within housing 52, as shown on figure 5. Screwing of nut 110 pushes assembly 50 towards the configuration of figure 4 where effort E firmly immobilizes support member 64 with respect to pin 30, by the cooperation between surfaces

68 and 72.

In order to facilitate its driving in rotation around axes X90 and X30, nut 110 is provided with four notches 184 adapted to receive a tool, such as the end of the stem of a screwdriver. In the working configuration of assembly 50 represented on figure 4, nut 110 protrudes from the end surface 186 of pin 30 on a distance O2, so that the notches 184 can be easily accessed. Therefore, no specific tool is to be used for screwing or unscrewing nut 110 in housing 52. The use of an elastically deformable washer to transmit effort E between nut

110 and ball bearing 100 allows to compensate for the possible variations of dimensions between the constitutive parts of assembly 50. In other words, washer

120 can accommodate differences in the dimensions of items 64, 80, 90, 100, 110 and 60. The invention is represented on the annexed figures with a washer having undulation. A Belleville washer, or any kind of elastically deformable washer, can also be used.

The overall structure of assembly 50 is such that the diameter of the part which deeply penetrates into pin 30 is relatively small, since it corresponds to the external diameter D ₉₀ of body 90. This diameter can be substantially smaller than the diameter of the parts used in the system of FR 2 904 671. Therefore, the internal diameter D ₅₂ of housing in the major part of its depth overall can be small, thus avoiding risks of breakage of pin 30.

The invention is represented on the figures with ball bearings 80 and 100. However, plain bearings, roller bearings or needle bearings could also be used.

Rolling bearings are preferred in order to keep the friction low.

The invention can be used with any instrumented joint provided with a pin, in particular in off-highway vehicles such as construction vehicles, e.g. backhoe loaders, excavators or wheel loaders, with agricultural vehicles, e.g. tractors and with mining vehicles, e.g. wheel loaders. The invention allows to determine the position of one arm with respect to another arm or to a chassis of such a vehicle.

The invention can also be used for the measurement of the angular position of a wheel such as a wheel of a truck or even a car.