Protective compound-enveloped sensor for detecting the position of an encoder element

Abstract

The sensor for detecting the position of a generator element which outputs a position-dependent physical variable, the sensor includes a transducer for converting the physical variable into an electric generator signal, a circuit on a wiring support for receiving the generator signal from the transducer and outputting a measurement signal that corresponds to the generator signal and a protective compound which at least partially surrounds the transducer and the wiring support, thus retaining the transducer on the wiring support.

Claims

1. A sensor for detecting a position of an encoder element, said sensor comprising a transducer having coil wires, a magnetic core having a length extending along an axis of the magnetic core, a circuit on a wiring carrier, and a protective compound comprising a thermosetting plastic material which at least partially envelops the transducer and the wiring carrier and thus holds the transducer on the wiring carrier, wherein the protective compound defines exactly four separating elements, each of the exactly four separating elements in direct contact with and extending outward from the magnetic core in an orthogonal direction relative to the axis of the magnetic core, the exactly four separating elements dividing the magnetic core along the length of the magnetic core into two outer winding regions and one inner winding region, the two outer winding regions each being shorter along the length of the magnetic core than the one inner winding region, and wherein the coil wires are wound around the axis of the magnetic core onto the magnetic core between respective ones of the exactly four separating elements that divide the magnetic core into each of the outer winding regions and between respective ones of the exactly four separating elements that divide the magnetic core into the inner winding region.

2. The sensor as claimed in claim 1, wherein the circuit on the wiring carrier comprises a part which is free of the protective compound.

3. The sensor as claimed in claim 1, wherein the transducer is an electrical transformer.

4. The sensor as claimed in claim 1, wherein the transducer is a linear inductive position sensor (LIPS).

5. The sensor as claimed in claim 1, wherein the protective compound forms an outer housing of the sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above-described properties, features and advantages of this invention and the way in which they are achieved will become clearer and more easily comprehensible in connection with the description below of exemplary embodiments, which are explained in more detail in connection with the drawings, in which:

(2) FIG. 1 shows a tandem master cylinder comprising a position sensor,

(3) FIG. 2 shows the position sensor from FIG. 1,

(4) FIG. 3 shows an interface at the position sensor shown in FIG. 2,

(5) FIG. 4 shows an alternative interface at the position sensor shown in FIG. 2,

(6) FIG. 5 shows another alternative interface at the position sensor shown in FIG. 2,

(7) FIG. 6 shows a converter in the position sensor shown in FIG. 2 in a first production state, and

(8) FIG. 7 shows a converter in the position sensor shown in FIG. 2 in a second production state.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(9) The same technical elements are provided with the same reference symbols and only described once in the figures.

(10) Reference is made to FIG. 1, which shows a tandem master cylinder 2 comprising a position sensor 4.

(11) The tandem master cylinder 2 also has a pressure piston 6, which is arranged movably in a movement direction 8 in a housing 10, wherein the movement of the pressure piston 6 can be controlled by a foot pedal (not shown). The pressure piston 6 itself is divided into a primary piston 12 and a secondary piston 14, wherein the primary piston 12 closes an inlet of the housing 10 and the secondary piston 12 divides the interior of the housing 10 into a primary chamber 16 and a secondary chamber 18. A secondary collar 20 is arranged in the region of the inlet of the housing 10 on the primary piston 12, which secondary collar insulates the interior of the housing 10 from the ambient air. When viewed into the interior of the housing 10, a primary collar 22 follows the secondary collar 20, said primary collar sealing a gap between the primary piston 12 and a wall of the housing 10. A pressure collar 24 on the secondary piston 14 isolates the pressure of the primary chamber 16 from the pressure of the secondary chamber 18. In addition, a further primary collar 26 on the secondary piston 14 seals a gap between the secondary piston 14 and the wall of the housing 10. The primary piston 12 is supported against the secondary piston 14 via a first spring 28, while the secondary piston is supported against a housing base via a second spring 30. Correspondingly, hydraulic fluid (not shown) can be supplied to the primary chamber 16 and the secondary chamber 18 via a first and second connection 32, 34.

(12) Since the mode of operation of a tandem master cylinder is known to a person skilled in the art, no detailed description thereof is provided here.

(13) The position sensor 4 has a sampling element in the form of a slide 36 comprising a sensor magnet 37 at its top end, which, when viewed into the plane of the drawing, can be pushed beneath a sensor circuit 38 (yet to be described). In order to push the slide 36, the primary piston 12 has a flange 40, which the slide 36 abuts. The flange 40 and the primary piston 12 therefore together form a measurement object, whose position is determined by the sensor circuit 38 (yet to be described) of the position sensor 4. The sensor circuit 38 is formed from a plurality of conductor tracks on a wiring carrier 42, such as a leadframe, a printed circuit board or another substrate. In order to protect against contamination, for example, a cover 46 can be positioned on the printed circuit board 42 with the sensor circuit 38.

(14) Reference is made to FIG. 2, which shows the position sensor 4 shown in FIG. 1.

(15) The circuit 38 of the position sensor comprises a transducer 48, which in the present embodiment is in the form of a linear inductive position sensor (LIPS). The transducer 48 detects a magnetic field 50 of the sensor magnet 37 and thereupon outputs an electrical sensor signal (not denoted) to the circuit 38 on the basis of this magnetic field. This sensor signal is converted by a first signal processing chip 52 and a second signal processing chip 54 into a measurement signal (not denoted), from which the position of the slide 36 and therefore the position of the flange 40 and the primary piston 12 is provided. The measurement signal thus produced can finally be tapped off at a transmission interface 56 of the position sensor 4 via a cable (not illustrated) and passed on to a higher signal processing unit (not illustrated) such as, for example, a motor controller in a vehicle (not illustrated).

(16) The circuit 38 can comprise protection elements 58 for protecting the two signal processing chips 52, 54, for example from an overvoltage. In addition, a shielding plate 60 can be arranged between the circuit 38 and the transducer 48, said shielding plate shielding electromagnetic fields between the circuit 38 and the transducer 48 and thus avoiding an influence of the circuit 38 on the transducer 48.

(17) In the present embodiment, the transducer 48 is arranged via a form-fitting connection 62 in a defined position on the wiring carrier 42. In this case, a protective compound 64, which holds the wiring carrier 42 and the transducer 48 mechanically together, the wiring carrier 42 and the transducer 48. In this way, the protective compound 64 can not only ensure a mechanical stability between the wiring carrier 42 and the transducer 48, but an interior of the position sensor 4 with the circuit 38 is also effectively protected from contamination. In this case, this interior can particularly preferably likewise be filled with the protective compound 64.

(18) The position sensor 4 can be encapsulated by injection molding, for example, with the protective compound 64 during production. For this purpose, the wiring carrier 42 of the position sensor 4 can be held on the transmission interface 56, for example, which in any case needs to remain free in order to make electrical contact with the abovementioned cable.

(19) This transmission interface 56 can be embodied differently, which is shown in FIGS. 3 to 5. According to said figures, the transmission interface can comprise contact bores 66 or edge group plugs 68. The transmission interface 56 can in this case also be surrounded by a wall 70 formed from the protective compound 64, as shown in FIGS. 2 and 5.

(20) Reference is made to FIG. 6, which shows the transducer 48 in the position sensor 4 from FIG. 2 in a first production state.

(21) In order to produce the transducer 48, which is to be in the form of an LIPS, a leadframe 72 with contact legs 74 is punched out for the first production state, said leadframe mechanically supporting the transducer 48 on the abovementioned wiring carrier 42 and making electrical contact between said transducer and the circuit 38 on the wiring carrier 42. For reasons of clarity, only some of the contact legs 74 have been provided with a reference symbol in FIG. 6.

(22) Then, a magnetic core 76 is arranged in the leadframe 72, said magnetic core later being provided for transmission of a magnetic field between coils (yet to be described).

(23) Reference is made to FIG. 7, which shows the transducer 48 in the position sensor 4 from FIG. 2 in a second production state.

(24) In order to produce the second production state shown in FIG. 7, the leadframe 72 is enveloped with the magnetic core 76 by a transducer protective compound 78. This transducer protective compound 78 in the present embodiment consists of a thermosetting plastic, which has a substantially identical coefficient of thermal expansion to the magnetic core 76, which can be produced from iron, for example. In the event of temperature fluctuations, hardly any mechanical stresses can be input into the magnetic core 76.

(25) The transducer protective compound 78 is in this case formed with four separating elements 80 such that they divide the magnetic core 76 into two outer winding regions 82 and an inner winding region 84. In this case, the outer winding regions 82 are shorter than the inner winding region 84.

(26) Then, if the transducer protective compound 78 has been cured, for example, the contact legs 74 can then be bent in the direction of a lower side of the transducer 48, as shown in FIG. 7.

(27) In order to finish the transducer 48, coil wires (not illustrated) are wound onto the transducer into the winding regions 82, 84. A primary coil is in this case wound beyond all of the winding regions 82, 84, whereas a physically identical secondary coil is wound on into in each case one of the outer winding regions 82.

(28) During operation of the transducer, an electrical AC voltage signal is applied to the primary coil, for example, which AC voltage signal should induce an identical output signal in the physically identical secondary coils via the magnetic core 76.

(29) If the sensor magnet 37 of the slide 36 now approaches one of the two secondary coils, it drives the magnetic core 76 into saturation. This results in a changed transmission behavior of the electrical AC voltage signal between the primary coil and the corresponding secondary coil, to which the sensor magnet 37 has got closer, which can be evaluated via the sensor circuit in a manner known to a person skilled in the art. In this way, the position of the sensor magnet 37 can be detected via the transducer 48.