Method for manufacturing a sensor device for detecting the wheel speed of a vehicle

Abstract

The invention relates to a method for manufacturing a sensor device (10) for detecting the wheel speed of a vehicle. The sensor device (10) comprises at least two sensors (14), a carrier element (12) for receiving the at least two sensors (14), and a leadframe (16) arranged on the carrier element (12) for electrically contacting the at least two sensors (14). Each sensor (14) has a sensor element for detecting a physical quantity. The method comprises the following steps: • Inserting the carrier element (12) with the leadframe (16) into the injection mold, with a fixing element (18), so that the carrier element (12) is fixed in the injection mold by the fixing element (18). • Inserting at least two sensors (14) into the carrier element (12) • Connecting at least two sensors (14) to the leadframe (16) • At least partially overmolding the carrier element (12), the at least two sensors (14) and the leadframe (16) with a molding compound, so that a housing (46) is formed.

Description

[0001] The invention relates to a method for manufacturing a sensor device for detecting the wheel speed of a vehicle.

[0002] Modern vehicles are equipped with a variety of sensors to make driving safer and more comfortable. Among these sensors are wheel speed sensors, which measure the rotation of a wheel. The measured wheel speed is used, for example, in anti-lock braking systems (ABS), which prevent the wheels from locking up by reducing brake pressure.

[0003] A sensor device typically comprises several individual components that are assembled. In what is usually the final step, the components are overmolded with a polymer, a so-called molding compound, to protect the sensor elements of the device from environmental influences. It is common practice for a fixing element attached to a carrier element to remain there.

[0004] The present invention is based on the objective of providing a method for manufacturing a sensor device for detecting the wheel speed of a vehicle, which provides a reliable assembly of the components of the sensor device as well as a sensor device protected against environmental influences.

[0005] To solve the problem, a method for manufacturing a sensor device for detecting the wheel speed of a vehicle is proposed. The sensor device comprises at least two sensors, a carrier element for holding the at least two sensors, and a leadframe arranged on the carrier element for electrically contacting the at least two sensors. Each sensor has a sensor element for detecting a physical quantity. The method comprises the following steps: • Inserting the carrier element with the leadframe into the injection mold, using a fixing element, so that the carrier element is fixed in the injection mold by the fixing element. • Inserting at least two sensors into the carrier element • Connecting at least two sensors to the leadframe • At least partially overmolding the carrier element, which contains at least two sensors, and the leadframe with a molding compound, so that a housing is formed.

[0006] The term sensor device refers to a device comprising a support element, a leadframe arranged on the support element, at least two sensors, and a housing in which the at least two sensors are arranged.

[0007] A sensor is understood to be a device comprising a printed circuit board (PCB), a sensor element mounted on the PCB, and a connection element mounted on the PCB. The PCB is preferably a printed circuit board (PCB). The connection element is preferably configured for supplying power to the sensor element and for signal transmission. The PCB, the sensor element, and the electrical connection are preferably at least partially enclosed by a sensor housing. The sensor housing is preferably made of a polymer.

[0008] A carrier element is defined as any component designed to accommodate sensors, comprising a leadframe and a fixing element for securing it in an injection mold. The carrier element is preferably made of a polymer.

[0009] A leadframe is a metallic conductor carrier consisting of four separate electrical conductors. The leadframe serves as an electrical connection for at least two sensors and for data transmission to a control unit. The leadframe is preferably stepped. It also preferably has contact surfaces for connecting the sensor terminals, with these contact surfaces being raised. The leadframe is preferably made of copper.

[0010] A sensor element is understood to be an element comprising an electronic circuit designed to detect a physical quantity, in particular a magnetic field. The magnetic field is generated by an encoder element, which has a circular shape and is arranged on a rotating body. Permanent magnets with alternating north and south polarity are arranged on the encoder element at a defined radius and at defined intervals. The electronic circuit detects the change in the magnetic field over time and generates an analog output signal. The sensor element is preferably designed as an AMR, GMR, or Hall sensor. The encoder element is preferably an encoder disk.

[0011] A fixing element is any element that is arranged on the carrier element and designed to hold the carrier element in the injection mold. The carrier element is preferably punch-shaped, particularly rectangular. The fixing element comprises a cylindrical body that extends from one side, particularly the underside, of the carrier element. A cuboid body is arranged on the side of the cylindrical body opposite the carrier element. The fixing element is preferably made of the same material as the carrier element. Alternatively, the fixing element is made of a different material than the carrier element.

[0012] The term "molding compound" refers to the material that is injected into the injection mold after the sensor device components have been inserted. Preferably, the molding compound at least partially surrounds the sensors, the support element, and the leadframe, forming a housing. The molding compound is preferably made of a polymer. Preferably, the molding compound and the support element are different polymers. Alternatively, the molding compound and the support element are made of the same polymer.

[0013] The advantage of the invention lies in the fact that a method is provided in which a sensor device is provided that is both compact and less susceptible to environmental influences such as dust or liquids.

[0014] Preferably, the fixing element melts onto the carrier element during at least partial overmolding with the molding compound, forming a gas- and liquid-tight housing for the sensors. The fixing element preferably melts in such a way that it forms a continuous physical structure with the molding compound. This has the advantage that the sensors and the leadframe of the sensor device are protected from environmental influences.

[0015] Furthermore, the fixing element has a collar, which melts during overmolding with molding compound and forms the gas- and liquid-tight housing for the sensors. The collar is a rib radially circumferential around the cylindrical body of the fixing element, preferably becoming thinner with increasing radius. The collar is preferably continuous. Alternatively, the collar is divided into segments, which are preferably arranged at equal intervals. After the fixing device is separated, the collar forms the boundary of the housing. This has the advantage of improving the bond between the molding compound and the fixing element, which is created by the melting of the fixing element.

[0016] Furthermore, the fixing element of the carrier element can be separated after melting. Preferably, the fixing element is separated immediately after the injection of the molding compound, particularly in the injection mold. Separation is preferably achieved by cutting, shearing, sawing, or laser cutting. This has the advantage of reducing the size of the sensor device, allowing it to be used in smaller installation spaces.

[0017] A cap is preferably arranged on the leadframe, the cap being designed for galvanic isolation of the leadframe and being positioned on the side opposite the first fixing element. The cap is preferably stepped, with ridges formed on a first side of the cap that spatially separate the electrical conductors of the leadframe from one another. Snap-in elements are preferably provided on the first side, the snap-in elements engaging with mating snap-in elements provided on the carrier element. The cap is preferably made of a polymer. This has the advantage that the electrical conductors of the leadframe are galvanically isolated from one another, thereby reducing the susceptibility to faults.

[0018] Furthermore, the cap can be designed as a stop in the injection mold, particularly against the mold wall, during the injection molding process. The cap preferably has two spacers on its second side, opposite the first side, with the spacers preferably extending from the second side in a cuboid shape. The spacers are preferably made of the same material as the cap. This has the advantage that the sensor device is additionally fixed in the injection mold, thus improving the manufacturing of the sensor device.

[0019] Preferably, the at least two sensors of the sensor device can include connection elements, wherein the connection elements are connected to the leadframe. A connection element preferably comprises at least two electrical conductors. The connection elements are preferably configured for supplying power to the sensors and for signal transmission. The connection elements are preferably made of copper. A coupling capacitor can preferably be provided between the two electrical conductors of a connection element. This has the advantage of simplifying the assembly of the sensor device.

[0020] Furthermore, a cable can be attached to the leadframe. This cable is preferably designed to supply power to the sensor device and transmit signals to a control unit. The cable is preferably made of copper. This has the advantage that the sensor device can be supplied with power or voltage, and signals can simultaneously be transmitted from the sensor device to a control unit.

[0021] The cable is preferably arranged on the side of the leadframe opposite the support element. The cable is preferably attached to the leadframe by crimping, welding, or soldering. This has the advantage of simplifying the cable's attachment to the leadframe and thus to the sensor device.

[0022] Furthermore, the at least two sensors can be arranged, and in particular fixed, in a mounting bracket, which can have locking lugs for the sensors. The mounting brackets are preferably arranged offset in the direction of extension of the sensor or the leadframe. This has the advantage of simplifying the mounting of the sensors in the carrier element.

[0023] Preferably, the material of the fixing element and the material of the molding compound can have the same material properties. These material properties preferably include melting point and / or density and / or electrical conductivity and / or coefficient of thermal expansion and / or temperature coefficient and / or thermal conductivity and / or viscosity and / or elasticity. This has the advantage of improving the bond between the fixing element and the molding compound.

[0024] Furthermore, a sensor device for detecting the wheel speed of a vehicle is proposed. The sensor device comprises at least two sensors, a carrier element for receiving the at least two sensors, a leadframe arranged on the carrier element for electrically contacting the at least two sensors, and a first fixing element for fixing the carrier element in an injection molding machine. Each sensor has a sensor element for detecting a physical quantity.

[0025] Further advantages and features will become apparent from the following description in conjunction with the attached drawings. These show: Fig. 1 A perspective view of a support element of the sensor device with fixing element and leadframe Fig. 2 a side view of the support element according to Fig. 1 Fig. 3a a perspective view of the first side of a cap Fig. 3b a perspective view of a second side of the cap Fig. 4a a perspective view of a sensor device with fixing element Fig. 4b a perspective view of the sensor device after detachment of the fixing element

[0026] In Fig. Figure 1 shows a sensor device 10. The sensor device 10 comprises a carrier element 12, two sensors 14, a leadframe 16 attached to the carrier element 12, a fixing element 18, and a cap 20. Cables 22 are attached to the leadframe 16 on the side opposite the carrier element 12. The cable 22 comprises several cable conductors 48. Connection elements 24 are attached between the leadframe 16 and the two sensors 14.

[0027] The sensor device 10 is a redundant wheel speed sensor. Due to its redundancy, it has two sensors 14, each comprising a sensor element for detecting a physical quantity and a connection element 24. The sensor elements determine, for example, the change over time of a magnetic field generated by a sensor element (not shown), such as an encoder disc with alternating permanent magnets. The connection elements 24 each comprise two electrical conductors, which serve to supply power to the sensor 14 and / or to transmit signals to a control unit (not shown).

[0028] The sensor device 10 is, as shown here, inserted into an injection molding machine (not shown) with an injection mold. Once all components, i.e., the sensors 14 in the carrier element 12, the connection elements 24 with the leadframe 16, the leadframe 16 with the cables, and the cap 20 over the leadframe 16, are arranged, the sensor device 10 is overmolded with a molding compound (not shown).

[0029] In Fig. Figure 2 shows the carrier element 12. The carrier element 12 comprises the fixing element 18, the leadframe 16, and the fixing receptacles 26. The fixing element 18 is arranged on the underside of the carrier element 12 and is shaped like a punch. The fixing element 18 comprises a cylindrical body 28 and a cuboid body 30 attached to it. The fixing element 18 can be inserted into a corresponding negative of the injection mold (not shown). This fixes the carrier element 12 in the injection mold.

[0030] The fixing element 18 also has a collar 32, the collar extending radially around the cylindrical body 28 of the fixing element 18. The collar is designed to melt and fuse with the molding compound, which has a temperature >100° Celsius, during injection molding, thus forming a continuous, gas- and liquid-tight physical structure. This gas- and liquid-tight structure is hereinafter also referred to as the housing 46. The diameter of the collar 32 decreases with increasing radius with respect to the longitudinal axis of the cylindrical body 28.

[0031] The leadframe 16 extends from the side of the support element 12 and perpendicularly away from the support element 12 and the fixing element 18. The leadframe 16 comprises several individual electrical conductors, corresponding to the number of electrical conductors in the connection elements 24 of the sensors 14. The leadframe 16 is stepped, with the angle of the step between the sections of the electrical conductors of the leadframe 16 extending perpendicularly to the fixing element 18 being essentially 45°. The leadframe 16 also has contact elements 34 for connecting the connection elements 24 of the sensors 14 to the leadframe 16.

[0032] The fixing receptacles 26 are formed on the side opposite the support element 18. They serve to hold the two sensors 14 and are preferably designed as locking lugs. The fixing receptacles 26 are arranged offset from each other, which allows the support element 18 to be made smaller.

[0033] Furthermore, the carrier element 12 has counter-locking means 40, which are designed to receive locking means 38 of the cap 20 and to form a positive and force-locking connection with the locking means 38.

[0034] In Fig. Figure 3a shows the cap 20 from a first side. The first side is preferably the underside of the cap 20. The cap 20, like the leadframe 16, is stepped. On the first side of the cap 20, webs 36 are formed, extending away from the first side of the cap 20. The webs 36 are designed to spatially and / or galvanically separate the electrical conductors of the leadframe 16 from one another.

[0035] Furthermore, locking elements 38 are provided on the first side of the cap 20. These locking elements 38 are designed as locking lugs, with the locking elements 38 engaging in corresponding counter-locking elements 40 of the carrier element 12. This allows the cap 20 to be attached to the carrier element 12 in a force-fit and form-fit manner.

[0036] In Fig. Figure 3b shows the cap 20 from a second side opposite the first side. On the second side of the cap 20, cuboid bodies 42, hereinafter also referred to as stops 42, are formed, extending away from the second side of the cap 20. The stop 42 is designed to firmly fix the sensor device 10 in the injection mold after the individual components have been assembled, in addition to the fixing element 18, by the stop 42 resting firmly against the mold wall. A cap collar 44 is formed around the stop 42. This extends away from the second side of the cap 20 and parallel to the stop 42, with its thickness decreasing with increasing distance. The cap collar 44 is designed to melt the molding compound during injection molding and to form a gas- and liquid-tight housing 46 with the molding compound.This is intended to prevent dirt or water from entering the sensor interior.

[0037] The following describes an example of a method for manufacturing the sensor device. The carrier element 12 is placed in the injection mold of an injection molding machine, with the carrier element 12 and the fixing element 18 being inserted into a negative mold that corresponds to the shape of the fixing element 18. This secures the carrier element 12 in the injection mold. The two sensors 14 are then inserted into the carrier element and attached, for example, by welding, to the leadframe 16, which is arranged on the carrier element 12. The cable conductors 48 of the cable 22 correspond to the number of electrical conductors of the leadframe 16 and are connected to the leadframe 16, for example, by welding. The cap 22 is then placed onto the leadframe 16 and the cable 22 and connected to the carrier element 12 by the locking elements 38 of the cap 22 engaging with corresponding locking elements 40 of the carrier element 12.The locking means 38 and the shape of the cap 22 fix the cap 22 in three directions, with the x-axis running parallel to the webs 36 and the z-axis parallel to the stops 42.

[0038] The injection mold is closed, and the previously listed elements located within the injection mold are firmly arranged in the mold by the clamping element 18 and the stop 42. The injection molding process then takes place, during which molding compound is injected into the injection mold. The collar 32 of the clamping element 18 and the cap collar 44 melt and fuse with the molding compound, forming a gas- and liquid-tight housing 46.

[0039] In Fig. Figure 4a shows the sensor device 10 produced after injection molding. Here, the fixing element 18 protrudes from the sensor device 10, which would require more installation space. By melting the collar 32 and forming the gas- and liquid-tight housing 46, the fixing element 18 of the carrier element 12 can be removed.

[0040] In Fig. Figure 4b shows the sensor device after the fixing element 18 has been separated. The fixing element 18 was separated, for example, by a shearing process. After separation, the area of ​​the collar 32 can be seen, which has melted and fused with the molding compound to form a gas- and liquid-tight housing 46. Reference symbol list: 10 Sensor device 12 support element 14 sensors 16 Leadframe 18 fixing element 20 caps 22 cables 24 connection elements 26 fixation shots 28 Cylindrical body of the fixing element 30 Cuboid body of the fixing element 32 collars 34 contact elements 36 bridges 38 Resting materials 40 Counter-resting devices 42 stops 44 cap collars

Claims

[1] Method for manufacturing a sensor device (10) for detecting a wheel speed of a vehicle, wherein the sensor device (10) comprises at least two sensors (14), a carrier element (12) for receiving the at least two sensors (14), and a leadframe (16) arranged on the carrier element (12) for electrically contacting the at least two sensors (14), wherein each sensor (14) has a sensor element for detecting a physical quantity, comprising the following steps: • Inserting the carrier element (12) with the leadframe (16) into the injection mold, with a fixing element (18), so that the carrier element (12) is fixed in the injection mold by the fixing element (18). • Inserting at least two sensors (14) into the carrier element (12) • Connecting at least two sensors (14) to the leadframe (16) • At least partially overmolding the carrier element (12), the at least two sensors (14) and the leadframe (16) with a molding compound, so that a housing (46) is formed. [2] Method according to claim 1, characterized by , that the fixing element (18) melts during the at least partial overmolding of the carrier element (12) with the molding compound, whereby a gas- and liquid-tight housing (46) for the sensors (14) is formed by the melting. [3] Method according to claim 2, characterized by , that the fixing element (18) has a collar (32), wherein the collar (32) melts during overmolding with molding compound and forms the gas- and liquid-tight housing (46) for the sensors (14) with the molding compound. [4] Method according to any one of the preceding claims, characterized by , that the fixing element (18) of the support element (12) is separated after melting. [5] Method according to any one of the preceding claims, characterized by , that a cap (20) is arranged on the leadframe (16), wherein the cap (22) is designed for galvanic isolation of the leadframe (16) and is arranged on the side opposite the fixing element (18). [6] Method according to any one of the preceding claims, characterized by , that the cap (20) is designed as a stop (42) in the injection molding tool, in particular against the injection molding tool wall, during injection molding. [7] Method according to any one of the preceding claims, characterized by , that the at least two sensors (14) of the sensor device (10) comprise connection elements (24), wherein the connection elements (24) are connected to the leadframe (16). [8] Method according to any one of the preceding claims, characterized by , that a cable (22) is arranged on the leadframe, wherein the cable (22) comprises several individual cable conductors (48). [9] Method according to any one of the preceding claims, characterized by, that the cable (22) is arranged on the side of the leadframe (16) opposite the support element (12). [10] Method according to any one of the preceding claims, characterized by that the at least two sensors (14) are arranged, in particular fixed, in a fixing receptacle (26), wherein in particular the fixing receptacles may have locking lugs for the sensors (14). [11] Method according to any one of the preceding claims, characterized by , that the material of the fixing element (18) and the material of the molding compound have the same material properties. [12] Sensor device (10) for detecting a wheel speed of a vehicle according to a method of the preceding claims, wherein the sensor device (10) comprises at least two sensors (14), a carrier element (12) for receiving the at least two sensors (14), a leadframe (16) arranged on the carrier element (12) for electrical contacting the at least two sensors (14) and a fixing element (18) for fixing the carrier element (12) in an injection molding machine, wherein each sensor (14) has a sensor element for detecting a physical quantity.

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