Wheel speed sensor Technical Field

The present utility model relates to the design of a wheel speed sensor, in particular, to a wheel speed sensor containing a Hall sensor element. Background Art

For the driving safety of a vehicle, the wheel speed (the rotating speed of wheels) is important monitoring data. The current driving state of a vehicle can be learned through wheel speed data so as to remind the driver to pay attention to the speed control of the vehicle or to be provided for a vehicle safety system to run corresponding safety auxiliary functions on the basis of the current driving state of the vehicle, thereby guaranteeing the safety of the people in the vehicle. With respect to reminding the driver, the wheel speed data can be converted into the speed of the vehicle by way of background computation and displayed on the instrument panel for the driver to view the current speed of the vehicle. However, with respect to the application of the vehicle safety system, an antilock braking function achieved by the antilock braking system (ABS), which is almost the standard configuration of all vehicles at present, is one of the relatively important functions in said safety auxiliary functions. It is known to all that the wheel locking condition often happens during emergency braking when the vehicle encounters an emergency during driving. This wheel locking condition will be disadvantageous to the normal braking of the vehicle and then endangers the driving safety. The antilock braking system can then determine whether the wheel has a locking tendency through real-time measurement to the wheel speed, and once established, the pressure in the brake cylinder of the vehicle will be adjusted to prevent the wheel locking condition from happening. Currently, the wheel speed sensor for measuring the wheel speed in real time gains extensive attention on the market because of its importance in achieving the abovementioned functions. To achieve more efficient wheel speed measurement, the existing wheel speed sensor generally adopts a contactless structure, wherein a wheel speed sensor containing a Hall sensor element also gains relatively extensive application. Therefore, how to make the performance of the wheel speed sensor containing the Hall sensor element more stable so as to provide a more accurate wheel speed measurement signal also becomes a focus of attention of the existing design.

Contents of the utility model

The problem to be solved by the present utility model is to provide a wheel speed sensor which is more stable in performance.

In order to solve the above problems, at least a sensor main body and a housing assembly are comprised, wherein said sensor main body comprises a Hall sensor element, a lead frame, a support and a wiring harness. Said lead frame, which is arranged in the support by way of injection molding, is provided with a lead connection structure for achieving the electric connection between said Hall sensor element and said wiring harness; said support is provided with a mounting slot which is adapted to said Hall sensor element, with said Hall sensor element being located in said mounting slot; said lead frame and support are en ^¬ capsulated in an insulation housing as a whole, with said insulation housing being fixed in said housing assembly; and a part of said wiring harness is located in said insulation housing.

Alternatively, said housing assembly comprises a housing main body, said housing main body is provided with a buckling structure adapted to said insulation housing; said insulation housing is buckled in said buckling structure to be fixedly connected to said housing main body. Compared with the prior art, the wheel speed sensor of the present utility model has the following advantages:

1) The position of said Hall sensor element is maintained fixed after completing the assembly of the wheel speed sensor by encapsulating the support and the lead frame assembled with the Hall sensor element in the same insulation housing as a whole and fixing same in said housing assembly via said insulation housing. Said Hall sensor element being in a fixed position will effectively maintain the measurement accuracy to the wheel speed, so that the wheel speed sensor is more stable in performance.

2) In an alternative solution, due to the assembled structure adopted by the sensor main body and the housing main body, when the sensor main body or the housing main body has something wrong, this can be realized by replacing the sensor housing main body or the housing main body, thereby saving the maintenance cost.

Description of the accompanying drawings

Fig. 1 is an overall schematic diagram of one embodiment of a wheel speed sensor of the present utility model;

Fig. 2 is an exploded schematic diagram of the wheel speed sensor shown in Fig. 1 ;

Fig. 3 is a schematic diagram of the connection of a support and a lead frame and a wiring harness of the sensor main body in the wheel speed sensor shown in Fig. 1 ;

Fig. 4a is an elaborated schematic diagram of one particular implementation of the sensor main body shown in Fig.

3;

Fig. 4b is an equivalent schematic diagram of a measurement signal processing circuit in the sensor main body shown in Fig. 4a; and

Figs. 5 to 8 are assembly schematic diagrams of the sensor main body shown in Fig. 3. Particular embodiments

The wheel speed sensor of the present utility model will be further described below through particular embodiments. Fig. 1 shows a particular structure of one embodiment of the wheel speed sensor of the present utility model. With reference to Fig.

1, said wheel speed sensor comprises a sensor main body 1, a housing assembly 2 and a signal panel 3. The three are assembled together through their respective connection mechanisms, and said sensor main body 1 is fixed in said housing assembly 2 to realize the real-time measurement to the wheel speed. Par ^¬ ticularly, said wheel speed sensor is fixed on the wheel through said signal panel 3. Said signal panel 3 rotates along with the rotation of the wheel. A magnetic field source is provided in said housing assembly 2, and said signal panel 3 rotates along with the wheel, resulting in the change of the magnetic field in said housing assembly 2. The sensor main body 1 will then generate a measurement signal on the basis of said change in the magnetic field, that is, the wheel speed data which is measured in real time. Based on the working process of said wheel speed sensor, since the sensor main body 1 is fixed in said housing assembly

2, the distance thereof relative to the signal panel also remains fixed, which will effectively maintain the measurement accuracy thereof to the wheel speed.

Fig. 2 shows an exploded schematic diagram of the wheel speed sensor shown in Fig. 1. The housing assembly and the signal panel in the abovementioned wheel speed sensor are described in detail below with reference to Fig. 2.

With references to Figs. 1 and 2 together, said housing assembly 2 comprises a housing main body 21, a central axis 22 and a permanent magnet 23. Said central axis 22 is provided with a mounting hole, and said permanent magnet 23 is fixed in said mounting hole as the magnetic field source. When said central axis

22 is fixed in said housing main body 21, said permanent magnet

23 can generate the abovementioned magnetic field in said housing main body 21. In order to realize the fixing of said central axis 22 in said housing main body 21, methods such as injection molding can be adopted to accommodate and fix said central axis 22 in said housing main body 21. That is, said central axis 22 and said housing main body are integrated as a whole by way of injection molding through molds. In order to mate with said central axis 22, said housing main body 21 formed by way of injection molding should be provided with an axle hole matching said central axis 22.

Said central axis 22 also serves as a connection part for assembling said signal panel 3 into said housing main body 21. As shown in Fig. 2, said signal panel 3 is provided with a central hole matching said central axis 22 in size. Said assembly can be realized by sleeving said signal panel 3 on said central axis 22. Of course, the method of assembly of said signal panel 3 and said housing main body 21 can also proceed in other ways known to a person skilled in the art and not described here. After said signal panel 3 is assembled to said housing main body 21, the magnetic field in said housing main body 21 can be changed through the rotation of the signal panel 3. It should be noted that in order to realize the rotation of said signal panel 3 in said housing main body 21, after being assembled to said housing main body 21, said signal panel 3 should keep a space from the opposite face of said housing main body 21. Hence, the design of the structure in which said signal panel 3 is located in said housing main body 21 can be particularly taken into consideration on the basis of the realization of this rotation function. For example, the structure in which said signal panel 3 is located in said housing main body 21 can be provided with protrusion structures as shown in Fig. 2. Since said permanent magnet 23 has been fixed in said housing main body 21 by said central axis 22, and does not rotate with said signal panel 3, when said signal panel 3 which is assembled in said housing main body 21 rotates with the wheel, said protrusion structures will cut the magnetic lines of force in the magnetic field, thereby changing the _r

magnetic field in said housing main body 21. Said change of the magnetic field, as described above, will be detected by said sensor main body 1, and then the abovementioned measurement signal is output. Apparently, the protrusion structures of said signal panel 3 should be located between the Hall sensor element and the permanent magnet 23 in the sensor main body 1 so as to realize the detection and output of the change of the magnetic field. In order to make the change of the magnetic field be measured more accurately by said sensor main body 1, said protrusion structures can surround a plurality of tooth-shaped structures uniformly distributed on the rotation surface of said signal panel 3, with the spaces among the tooth-shaped structures being the same. Of course, the wheel speed sensor of the present utility model does not define the shape of said protrusion structures, and a person skilled in the art can also adopt other appropriate designs to realize the function of cutting the magnetic lines of force of said signal panel 3.

For the purpose that said wheel speed sensor as a whole has better sealing performance after said signal panel 3 is assembled in said housing main body 21, an oil seal 4 can be additionally provided on said housing main body 21. Said oil seal 4 adopts a rubber outside and a metallic framework in the middle, and the shape and size thereof should be fitted with a corresponding sensor mating hole of the wheel. The structure of said oil seal 4 can ensure that lubricating oil in the sensor is prevented from spilling and foreign impurities are prevented from entering the sensor during the rotation of the wheel, thereby prolonging the service life of said wheel speed sensor.

Fig. 3 shows a schematic diagram of the connection of a support and a lead frame and a wiring harness of the sensor main body in the wheel speed sensor shown in Fig. 1. The particular structure of the sensor main body is described in detail below in com- bination with Fig. 3. With reference to Figs. 1 and 3 together, said sensor main body 1 comprises a Hall sensor element 11, a lead frame 12, a support 13 and a wiring harness 14. Said lead frame 12 is provided with a lead connection structure for realizing the electric connection between said Hall sensor element 11 and wiring harness 14. The number of connection terminals in said lead connection structure which are electrically connected to said Hall sensor element 11 is correspondingly configured on the basis of the number of terminals and the work requirements of said Hall sensor element 11 itself; and the number of connection terminals in said lead connection structure which are electrically connected to said wiring harness 14 is correspondingly configured on the basis of the work requirements of said Hall sensor element 11 and the output requirements of the wiring harness 14. Said lead frame 12 is made of electric conducting materials such as metal and so on.

Said support 13 is provided with a mounting slot which is adapted to said Hall sensor element 11, the connection terminals of said lead connection structure are provided in the support by way of injection molding, and said Hall sensor element 11 is located in said mounting slot. The measurement signal generated by said Hall sensor element 11 is transmitted, via said connection terminals, to the wiring harness 14 and output for a corresponding vehicle control unit to determine the current state of the vehicle and take corresponding control measures, or for a corresponding vehicle instrument to read the current speed.

Fig. 4a shows a detailed schematic diagram of a particular implementation of said sensor main body. With reference to Fig. 4a, said sensor main body further comprises a measurement signal processing circuit which connects said Hall sensor element 11 and said wiring harness 14 via the connection terminals of said lead frame 12, and processes a measurement signal generated by said Hall sensor element 11 and then transmits same to said wiring harness 14. Particularly, taking said Hall sensor element 11 being a three-terminal (a power supply terminal, a ground terminal and an output signal terminal) sensing element as an example, with reference to Figs. 4a and 4b together, said measurement signal processing circuit comprises a resistor Rl connected at the power supply terminal of said Hall sensor element 11, a first capacitor CI connected in parallel between the output signal terminal and the ground terminal of said Hall sensor element 11, and a second capacitor C2 connected in parallel between the power supply terminal and the ground terminal of said Hall sensor element 11. The two-capacitor arrangement of said measurement signal processing circuit is beneficial for filtering a measurement signal output by said Hall sensor element 11 to strengthen the anti-interference of said wheel speed sensor.

Corresponding to the terminal configuration of said Hall sensor element 11, the number of connection terminals of said lead frame 12 which are electrically connected to said Hall sensor element 11 is 3, and the number of connection terminals which are electrically connected to said wiring harness 14 is at least 3. The resistor and capacitors in said measurement signal processing circuit each realize the circuit structure as shown in Fig. 4b by being electrically connected to corresponding connection terminals. Accordingly, said wiring harness 14 also at least comprises a power line, a ground line and an output signal line.

With reference to Figs. 3 and 4a together, said support 13 can also be provided with a mounting slot adapted to said resistor Rl, capacitor CI and capacitor C2. Firmer assembly of said measurement signal processing circuit in said sensor main body can be realized through the mounting slot of said resistor and capacitors .

For example, Figs. 5 to 8 show an instance of assembly based on the structure of said support 13. At first, with reference to Fig. 5, the connection terminals of said lead frame 12 are arranged in said support 13 by way of injection molding through molds. _n

Also, said Hall sensor element 11 is placed in a corresponding mounting slot, and all the terminals of said Hall sensor element 11 and corresponding connection terminals of said lead frame 12 are fixed together by welding after being countered.

Next, with reference to Fig. 6, said resistor Rl is placed in a corresponding mounting slot, and based on the circuit structure of Fig. 4b, both ends of said resistor Rl are respectively welded with corresponding connection terminals of said lead frame 12 so as to realize the electric connection of said resistor Rl with the power supply terminal of said Hall sensor element 11 as well as the electric connection with the connection terminals connected to said power line in said lead frame 12. Then, with reference to Fig. 7, the capacitor CI and the capacitor C2 are respectively placed in corresponding mounting slots, and based on the circuit structure of Fig. 4b, the respective terminals of the capacitor CI and the capacitor C2 and cor ^¬ responding wiring harnesses are commonly placed in corresponding connection terminals of said lead frame 12 and are pres ^¬ sure-welded together. For example, for one end of the capacitor CI which is grounded, this end and the ground line are placed in corresponding connection terminals of the lead frame and are pressure-welded together.

Finally, integrated injection molding is performed by designing molds, said lead frame 12 and support 13 are encapsulated in the same insulation housing as a whole, that is, a sensor main body as shown in Fig. 8 is formed. A part of said wiring harness 14 is encapsulated in said insulation housing, and another part of said wiring harness 14 is located outside said insulation housing so as to realize the connection with a vehicle control unit or a vehicle instrument outside. The way in which all the components in the sensor main body except a part of the wiring harness are encapsulated in the same insulation housing by integrated injection molding can make said wheel speed sensor have very good anti-vibration and sealing performance so as to be adapted to the driving conditions of the vehicle under different road situations .

To make the description more concise, two opposite faces of said support 13 assembled with the resistor and capacitors are called assembling faces, and the other two opposite faces are called side faces. The part of the opposite side faces of said insulation housing is called a side wall. With reference to Figs. 3 and 8 together, said support 13 is located at the side wall of said insulation housing, that is, said side face is provided with a plurality of protrusions. Said protrusions adopt a material with a melting point lower than the injection molding temperature, and during injection molding, said protrusions will melt and are integrated with the insulation housing. This structure setting enhances the sealing performance of the sensor main body, and because said insulation housing itself has waterproof capa ^¬ bility, this structure also ensures that internal components of the sensor main body have a relatively good waterproof capa ^¬ bility. Said protrusions are cusp-shaped and distributed around corresponding fixed points in the sensor main body.

With reference to Figs. 1, 2 and 8 together, the sensor main body as shown in Fig. 8 is inserted into said housing main body 21 in a way as shown in Fig. 2, the oil seal 4 is pressed into said housing main body 21, and said signal panel 3 is sleeved on said central axis 22 so as to be assembled into said housing main body 21 to complete the overall assembly of said wheel speed sensor and form a wheel speed sensor as shown in Fig. 1. In a more optimized design, a buckling structure can also be provided in said housing main body 21 so as to make said sensor main body and said housing main body 21 fix together through the buckling structure. When the sensor main body breaks down, said sensor main body can be pulled out from the buckling structure, making said sensor main body and the housing main body easy to replace. It can be seen from the overall assembling process that said signal panel is also easy to replace. Taking said wheel speed sensor being applied to a motorcycle as an example, two claw structures can be arranged at the parts of said signal panel relative to the wheels of the motorcycle. Accordingly, when the wheels of the motorcycle rotate, the signal panel and the wheels can be poked to rotate synchronously. The rotation of the signal panel, as mentioned above, can make the protrusion structures thereon cut the magnetic lines of force of the magnetic field in said buckling main body so as to make the magnetic field change. The Hall sensor element in said sensor main body will detect this change and generate a measurement signal. Said measurement signal is output to the instrument panel through said wiring harness, and the speed value obtained after cal ^¬ culating through said instrument panel is displayed on the instrument panel.

Although the present utility model is disclosed as above in the preferred embodiments, the present utility model is not limited to this. Various alterations and modifications made by anyone skilled in the art without departing from the spirit and scope of the present utility model should be included in the scope of protection of the present utility model; therefore, the scope of protection of the present utility model should subject to the scope defined by claims.