KR20070093609A - Torque sensing device of electric power steering - Google Patents

Abstract

A torque sensing device of an electric power steering is provided to block the influence from a nearby magnetic subject by not measuring the torque from the amplitude of the measured voltage. A torque sensing device of an electric power steering includes a torsion bar, at least one inducing device(20), and at least one sensing part(30). The inducing device includes a coupling part(21) and an inducing body(22). The sensing part includes an inducing part(31) and a detecting part(32). The torsion bar connects an input axis and an output axis at one axis. The inducing device is coupled to one side of the torsion bar and generates inducing currents. The sensing parts are placed at a certain interval on the inducing part and induce induction currents to the inducing part to measure the magnetic field varied by the inducing part which rotates with the torsion bar. The coupling part is coupled at a certain place of the outer circumference of the torsion bar and the inducing body is extended from the coupling part. The inducing body induces currents and the detecting part measures the rotating angle and torque.

Description

Torque Sensing Device Of Electric Power Steering

1 is a block diagram of a conventional magnetoresistive torque detecting device of a magneto-resistive type.

2 is a configuration diagram of a magnetic torque detection device of a conventional magneto-strict type.

3 is a cross-sectional view showing a torque detection device according to an embodiment of the present invention.

4 is a cross-sectional view showing a torque detection device according to another embodiment of the present invention.

5 is a sectional view seen from the side of the torque detection device according to another embodiment of the present invention.

6 is a cross-sectional view showing a torque detection device according to another embodiment of the present invention.

7 is a cross-sectional view showing a torque detection device according to another embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

10: torsion bar 20: guide member

21: conjugate 22: derivative

30: sensing unit 31: here

32: detector

The present invention relates to an electric steering torque detection device for a vehicle using the principle of induction current. The present invention relates to an electric steering torque detection device capable of ensuring measurement accuracy even when foreign matter is introduced or temperature is changed, and can prevent a change in measured value due to proximity of a magnetic material.

In general, a steering shaft of a vehicle in which a power steering device is installed is composed of an input shaft and an output shaft, a dual input shaft is coupled to a steering wheel side, and an output shaft is coupled to a pinion gear side coupled with a rack bar of a tie rod.

The input shaft and the output shaft are connected by a torsion bar. In this structure, when the steering wheel is rotated, the output shaft rotates, and the direction of the wheel coupled to the tie rod is changed by the gear action of the pinion gear and the rack bar.

At this time, when the ground resistance between the wheel and the road surface is large, the gear action between the rack bar and the pinion gear is also not smoothly performed, and the output shaft combined with the pinion gear side rotates less than the input shaft combined with the steering wheel side. Twisted.

The twist degree of the torsion bar is input to the electronic control unit in an electric signal state, and the ECU operates the auxiliary power unit installed in the rack bar based on this signal to compensate for the rotation of the output shaft so that the steering wheel operation force is improved. In this case, the torsion bar torsion detection is performed by the torque sensor.

The torque sensors used in the electric power steering system can be classified into two types, one of which is a torque method that directly measures the deformation of the torsion bar by using a strain gauge and a potentiometer. The sensor is classified into a sensor that indirectly measures the deformation of the torsion bar in a non-contact method, magnetically and optically.

The double contact torque sensor is inferior to the non-contact type in terms of noise and durability, so the non-contact torque sensor is mainly used.

In general, a non-contact optical torque sensor is attached to a torsion bar and has two discs or one disc perforated to induce a change in the amount of light or pattern when the light emitted from the emitter passes through the disc and measure the torque with this difference. In addition, the rotation angle can be measured with the number of optical pulses.

However, since the optical torque sensor measures the torque with the amount of light, it may cause a malfunction if a foreign material penetrates the light that may interfere with the progress of the light. In particular, the use of an optical torque sensor in a vehicle has a big problem because a vehicle is very likely to penetrate foreign matters while driving, and foreign matters are generated by corrosion and wear of an operating part.

Hereinafter, the magnetic torque sensor will be described with reference to the accompanying drawings. 1 is a block diagram of a conventional magnetoresistive type magnetic torque detecting device, and FIG. 2 is a block diagram of a conventional magneto-strictive type magnetic torque detecting device. As shown in FIGS. 1 and 2, the magnetic torque detecting device 9 is largely classified into two types, magneto-resisttive and magneto-strictive.

Here, the torque sensing device 9 of the magnetoresistive MR type of FIG. 1 is torqued by using one to three toothed measuring rings 3 or measuring rings 3 of which the polarity is continuously arranged in the N pole S pole. The torque is measured with an inductance of the adjacent sensing means 5 which induces a change in the magnetic field and changes according to the change in the magnetic field.

The magnetoresistance type structure has a large number of teeth of the measuring ring 3 arranged on the torsion bar 1, which requires precise work in the processing and assembly of the measuring unit, thereby increasing the defect rate during manufacturing and assembling the produced product. Depending on the condition, the deviation between the output signal characteristics of the products is likely to be large.

In particular, in the case of automotive sensors, accurate measurement is required even at a temperature change of about -40 ° C to 135 ° C depending on the mounting environment. In the case of the Magneto-Resistive type, the magnetic property of the magnetic material is changed to heat. A large point is highlighted as a weak point, making accurate measurement within the above temperature range difficult.

In addition, there is a high possibility that an error may occur due to the change of the magnetic field of the sensing site due to magnetization of the surrounding metal material during use.

In addition, the torque sensor of the magnetostriction type of FIG. 2 measures the torque as a change in inductance according to the magnetic field change of the sensing stage adjacent to the torsion bar 1, and the magnetostrictive type of the magnetoresistive torque sensor 9 It is similar to), but it uses a material whose magnetic property changes with respect to stress to induce the change of magnetic field according to the change of magnetic property.

In the case of such a magnetostriction type, as in the magnetoresistance type, there is a problem in that accurate measurement is difficult due to temperature change and a problem in which the rotation angle cannot be measured.

The present invention has been made in order to solve the above problems, the induction member to which the induction current flows by the sensing unit is fixedly coupled to the torsion bar and by detecting the magnetic flux changes by the induction member through the sensing unit, foreign matter is introduced or temperature is changed. Even if the measurement accuracy can be ensured, and the purpose is to provide an electric steering torque detection device that can prevent the change of the measurement value in accordance with the proximity of the magnetic material.

The present invention has the following features to achieve the above object.

The present invention relates to an apparatus for detecting a steering torque having a structure in which the input shaft and the output shaft are connected by a torsion bar and a torque displacement between the input and output shafts is generated by a load applied to the output shaft when an input torque is applied.

A torsion bar connecting the input shaft and the output shaft coaxially; and at least one induction member coupled to one side of the torsion bar and generating an induction current; and arranged at a predetermined interval apart from the induction member and inducing the induction member. And at least one sensing unit for exciting a current and measuring a magnetic field that is changed by an induction member which is rotated together with the torsion bar.

In addition, the induction member comprises a coupling coupled to the outer edge of a certain point of the torsion bar, and a derivative extending to the coupling so as to be arranged parallel to be spaced apart by a predetermined distance along the outer edge of the torsion bar, the outer edge of the torsion bar A pair of induction members are disposed to face each other, and a distance from the torsion bar is different, and a pair of induction member derivatives are positioned on the same center line of the torsion bar, respectively.

In addition, the sensing unit comprises a detection unit for measuring the rotation angle and torque by measuring the magnetic field that is changed by the excitation body and the induction member to generate an induction current in the induction member.

Hereinafter, the torque detection device according to the present invention will be described in detail together with the accompanying drawings.

3 is a cross-sectional view showing a torque detection device according to an embodiment of the present invention, Figure 4 is a cross-sectional view showing a torque detection device according to another embodiment of the present invention, Figure 5 is a torque according to another embodiment of the present invention 6 is a cross-sectional view of a torque detector according to still another embodiment of the present invention, and FIG. 7 is a cross-sectional view of a torque detector according to another embodiment of the present invention.

Referring to the drawings, the torque detection device according to the present invention is largely coupled to the torsion bar 10 that connects the input shaft and the output shaft coaxially, and at least one induction coupled to one side of the torsion bar 10, the induced current is generated A magnetic field that is disposed by the member 20 and the induction member 20 spaced apart from the induction member 20 by the induction member 20 that excites the induction current to the induction member 20 and rotates together with the torsion bar 10. It consists of at least one sensing unit 30 for measuring the.

Here, the torsion bar 10 is coaxially connected to the input shaft and the output shaft, and configured to co-rotate according to the rotation of the steering wheel connected to the input shaft.

The torque detecting device according to the present invention can detect the degree of deformation by the rotation of the torsion bar 10 to compensate for the rotation of the output shaft by the power of the auxiliary power unit.

The induction member 20 is fixedly coupled to the torsion bar 10, wherein the induction member 20 is coupled to a certain point of the periphery of the torsion bar 10 and the torsion bar 10. It is composed of a derivative 22 extending to the assembly 21 so as to be spaced apart at a certain distance along the outer edge in parallel.

Here, the assembly 21 is formed in a disk shape having a hollow, and the diameter of the hollow is formed by a predetermined length smaller than the outer diameter of the torsion bar 10 is configured to be fixed by pressing or to the assembly 21 and torsion The bar 10 may be configured to be fixed by welding or the like.

In addition, the derivative 22 is formed on one side of the circumferential surface of the combination 21 to be spaced apart by a predetermined distance, and the derivative 22 is disposed parallel to the outer edge of the torsion bar 10 at a predetermined distance.

In addition, the derivative 22 is induced current is generated by the excitation body 31 of the sensing unit to be described later, the derivative 22 and the combination 21 is of course a metal material such as steel or aluminum.

In addition, the sensing unit 30 is provided to excite the induction current to the induction member 20, and thus to measure the torque applied to the torsion bar by detecting a change in magnetic flux caused by the induction current, wherein the sensing unit 30 Is composed of an excitation body 31 for generating an induction current in the induction member 20 and a detection unit 32 for measuring a rotation angle and torque by measuring a magnetic field changed by the induction member 20.

The excitation body 31 and the detection unit 32 are preferably configured in the form of a coil, and the detection unit 32 constitutes a bridge circuit.

The principle of measuring the rotation angle and torque through the induction member 20 and the sensing unit 30 is an induction current, and the principle of the induction current conducted to the derivative 22 is as follows.

In general, when an alternating current is applied to a coil, a magnetic field (alternating magnetic field) that changes formally around the coil is generated. In this case, if a conductor exists in the alternating magnetic field, the magnetic field changes in time, so electromotive force is generated by the law of electromagnetic induction and current flows in the conductor. This current is called induction current.

This principle has already been used to detect various defects in conductor structures such as corrosion of heat exchanger tubes in power plants or chemical devices.

Referring to the principle of torque detection in the torque detecting device according to the present invention, if the excitation body 31 is formed to be spaced apart a certain distance as shown in Fig. Magnetic flux is generated and thus induced current is generated in the derivative (22).

This induces a change in the magnetic flux to change the inductance of the detector 32 close to the excitation body 31, and the change of the inductance is measured as a voltage using a bridge circuit.

That is, the rotation angle measurement by the steering wheel may be calculated by the following equation in proportion to the rotation angle of the torsion bar 10.

{360 ° / (number of derivatives × 2)} × voltage change = rotation angle

Meanwhile, in order to measure the torque value applied to the torsion bar 10, a pair of induction members 20 are disposed on the outer edge of the torsion bar 10 as shown in FIG. 4, but the separation distance from the torsion bar 10 is measured. Differently, a pair of induction member derivatives 22 are configured to be positioned on the same center line of the torsion bar 10, respectively.

Accordingly, when the torsion bar 10 is deformed due to torque, the inductor 22 disposed on the same center line is displaced due to the deformation of the torsion bar 10, which is a slight change in voltage generated by the same principle as above. Causes the interval to occur. That is, the torque value can be detected at this time interval.

Here, the sensing unit 30 and the inductor 22 are required to maintain the distance as close as possible for the accuracy of the measurement, in consideration of the influence of the vibration of the car, the preferred separation distance is 1mm to 10mm.

In addition, as shown in FIG. 7, the number of the sensing units 30 may be arranged at a plurality of points separated from the derivative 22 in order to increase measurement accuracy.

In addition, the number of derivatives 22 extending from the binder 21 can be varied as necessary, and 10 to 50 is preferable for accurate measurement of the rotation angle.

In addition, the cross-sectional shape of the inductor 22 may have a triangular or trapezoidal shape in order to accurately measure the torque. The longer the length of the inductor 22 is, the more accurate the measurement is, but preferably 100 mm to 200 mm due to the limitation of the structure. Preferably, the derivative 22 and the sensing unit exciter 31 are disposed perpendicular to the coil axis.

As described above, the torque detecting device according to the present invention can measure the rotation angle by installing one induction member 20 as shown in FIG. 3, and the rotation angle and torque by installing a pair of induction members as shown in FIG. 4. Quantity can be measured.

In addition, as shown in FIG. 6, the induction members are separated from each other by the torsion bar 10, and the sensing parts corresponding thereto may be used to measure the rotation angle and the torque, and as shown in FIG. 7. The length of formation of the derivative 22 of 20) may be further extended to configure more than one sensing unit 30 so that more accurate measurement may be made.

On the other hand, it has been described in the embodiment shown in Figures 3 to 7, but this is only illustrative and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. .

Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described above, the present invention is fixed to the torsion bar by inducing member through which the induced current flows by the sensing unit and detects the magnetic flux that is changed by the inducing member through the sensing unit to ensure measurement accuracy even if foreign matters are introduced or the temperature is changed. can do.

Also, the torque is not measured by the amplitude of the measured voltage, so it is not affected even when the magnetic object is close.

In addition, since the metal material generally used as a material constituting the measurement mechanism is used, the material cost can be reduced.

Claims (4)

In the steering torque detecting device having an structure in which an input shaft and an output shaft are connected by a torsion bar 10, and a torque displacement between the input and output shafts is generated by a load applied to the output shaft when an input torque is applied. A torsion bar 10 connecting the input shaft and the output shaft coaxially; At least one induction member 20 coupled to one side of the torsion bar 10 and generating an induction current; At least one or more spaced apart from the induction member 20 to excite an induction current to the induction member 20 and measure a magnetic field that is changed by the induction member 20 which is rotated together with the torsion bar 10. Electric steering torque detection device comprising a; sensing unit (30). The method of claim 1, The induction member 20 extends to the combination 21 so that the coupling body 21 is coupled to the outer edge of the torsion bar 10 at a predetermined point, and is parallelly spaced apart by a predetermined distance along the outer edge of the torsion bar 10. Electric steering torque detection device comprising a derivative 22 to be made. The method of claim 2, A pair of induction members 20 are disposed on the outer edge of the torsion bar 10 so as to have a different distance from the torsion bar 10, and a pair of induction member derivatives 21 are torsion bars 10, respectively. Electric steering torque detection device, characterized in that located on the same center line of the. The method of claim 1, The sensing unit 30 includes an excitation body 31 for generating an induction current in the induction member 20 and a detection unit 32 for measuring a rotation angle and torque by measuring a magnetic field changed by the induction member 20. Electric steering torque detection device, characterized in that made.

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