KR101177657B1 - Non-contacting type torque sensor for steering system - Google Patents

Abstract

The present invention relates to a non-contact torque sensor for a steering apparatus, comprising: a magnetic force generating unit having an upper magnet ring and a lower magnet ring in which a plurality of N pole magnets and S pole magnets are alternately arranged in a circumferential direction along an outer circumferential surface thereof; Magnetically provided with a plurality of shielding rods disposed at equal intervals corresponding to either the N-pole magnet or the S-pole magnet around the outer periphery of the magnetic force generating unit, and a single connection ring integrally formed with each shielding rod portion. A shield; The magnetic collecting unit is disposed on a radially outer side of the magnetic shield and includes upper and lower magnetic collecting rings for collecting magnetic flux passing through the plurality of shielding rods, and upper and lower magnetic collecting terminals extending from upper and lower magnetic collecting rings. part; And a magnetic detection sensor unit positioned between the upper and lower house terminals. As a result, a plurality of shielding rods and connecting rings, which are magnetic circuit parts belonging to the magnetic shield part, are integrally formed with each other to form a closed circuit, thereby enabling measurement of magnetic characteristics thereof.

Description

Non-contact torque sensor for steering system {NON-CONTACTING TYPE TORQUE SENSOR FOR STEERING SYSTEM}

The present invention relates to a non-contact torque sensor for a steering apparatus, and more particularly, a steering apparatus for improving steering power by allowing an output shaft connected to a wheel to be rotated in the same manner as the input shaft when the input shaft is rotated by the steering wheel. It relates to a non-contact torque sensor for use.

The present invention corresponds to an improved invention of the patent application No. 2008-0060701 (filed date: June 26, 2008) "non-contact torque sensor for steering apparatus" filed by the present applicant.

According to the prior patent application, as shown in Figure 1, the torque sensor 100 is disposed in the upper and lower covers 101 and 102, these covers 101 and 102 to protect the magnetic circuit of the sensor, Magnetic flux generated from the magnetic force generating unit 110 having the lower magnet rings 111 and 112, the magnetic shielding unit 120 having the magnetic shield ring 121, and the upper and lower magnet rings 111 and 112 ( Magnetic collector 130 having upper and lower magnetic flux collecting rings 131 and 132, which are magnetic circuit components for inducing magnetic flux to the magnetic detection sensor unit 140, and a Hall sensor for outputting a change amount of magnetic flux as a voltage value. It includes a magnetic detection sensor unit 140 including a (141).

To briefly describe the sensing mechanism of the torque sensor 100, the magnetic force generated in the upper and lower magnet rings 111 and 112, which are permanent magnets that are magnetized in multiple poles, is opened in the magnetic shield ring 121 located outside thereof. The Hall sensor 141 outputs a voltage value corresponding to the magnetic flux through a series of processes that are magnetically induced through the window 121a and through the magnetic flux collecting rings 131 and 132 to the periphery of the Hall sensor 141.

Torque sensor 100 having such a mechanism is characterized in that the magnetic characteristics represented by the upper and lower magnet rings 111 and 112, the magnetic shield ring 121 and the magnetic flux collecting rings 131 and 132, which are permanent magnets. Therefore, a large amount of deviation occurs in the performance of the entire sensor.

Therefore, inspecting the magnetic properties of each component prior to the manufacture of the torque sensor 100 is the basis of the production of the torque sensor.

The magnetic shielding torque sensor 100 is a magnetic circuit component used therein, and a permanent magnet (i.e., upper and lower magnet rings 111 and 112), which is a hard magnetic material having a coercive force characteristic of 1 kA / m or more, and a coercive force characteristic of 1 kA. Magnetic shielding ring 121 and upper and lower magnetic flux collecting ring (131, 132) made of a soft magnetic material of less than / m.

Such magnetic materials have magnetic hysteresis curves corresponding to the respective materials, and greatly affect the resolution, linearity, hysteresis, etc., which are important characteristics of the torque sensor 100, according to the magnetic hysteresis characteristics.

Here, the magnetic shield ring 121 and the magnetic flux collecting rings 131 and 132 using a soft magnetic material having a coercive force characteristic of less than 1 kA / m take a structure that must be deformed into various shapes in the process of designing a magnetic circuit.

That is, these soft magnetic materials are generally subjected to primary processing such as press working of steel sheet material, and then subjected to post processing such as heat treatment so as to have inherent magnetic properties of the soft magnetic material.

As described above, the soft magnetic materials having the final magnetic properties by the post-processing change the magnetic history curve, which is a basic characteristic of the magnetic material, due to factors such as heat treatment conditions and external force applied to the product after the heat treatment.

Therefore, in the manufacture of the torque sensor 100 to check the magnetic properties of such a soft magnetic material can be said to be an important manufacturing process.

On the other hand, the magnetic properties of the soft magnetic material is a method of measuring the magnetic properties by the Epstein method, a magnetic property measuring method by a single steel sheet tester, a ring-type magnetic property measuring method performed on a closed magnetic circuit.

Both the Epstein method and the method using a single steel plate tester are methods for measuring magnetic properties using standardized samples, and thus are not suitable for measuring magnetic properties of magnetic circuit components of soft magnetic materials presented by the torque sensor 100 to which the present invention belongs. Do.

In other words, in order to measure the magnetic characteristics of the part design of the soft magnetic material used in the torque sensor 100 to which the present invention belongs, it is preferable to use the magnetic characteristic measurement method by the ring method in the closed magnetic circuit.

FIG. 3 is a circuit used for measuring magnetic properties by a ring method for soft magnetic materials, and the contents of the KS standard and the IEC international standard (see below) are cited.

IEC 60404-4 "Magnetic materials-Part 4: Methods of measurement of D.C. magnetic properties of magnetically soft materials"

-IEC 60404-6 "Methods of measurement of the magnetic properties of isotropic nickel-iron soft magnetic alloys, types E1, E3, and E4"

-KS C IEC 60404-4 "Magnetic materials-How to measure the DC magnetic properties of soft magnetic materials"

-KS C IEC 60404-6 "Measuring magnetic properties of isotropic nickel-iron soft magnetic alloys"

4 is a hysteresis curve of magnetic properties of the magnetic material, and all kinds of magnetic materials have similar magnetic history characteristics.

In the case of soft magnetic materials having a coercive force of less than 1 kA / m, the coercive force characteristics that maintain or lose magnetic properties due to the external environment are different.

Therefore, in the torque sensor constituting the magnetic circuit using the soft magnetic material having such hysteresis characteristics, there is a marked difference in the performance of the sensor according to the magnetic hysteresis characteristics of the soft magnetic material.

In general, the torque sensor used in the MDPS (Motor Driven Power Steering) system has an operating range of less than ± 10 degrees. Therefore, the sensor must be sensed even during a small operating period and a short operating time. Can not satisfy the performance.

In addition, in general, the soft magnetic material is processed by the shape to make the product and then subjected to a separate heat treatment to optimize the magnetic properties of the soft magnetic material, and also in the case that the magnetic history characteristics change by external force after heat treatment It is also unusual.

Therefore, prior to fabricating the torque sensor using the soft magnetic material, the task of checking the magnetic properties of the soft magnetic material will serve as an important indicator of the performance of the product.

3 and 4 illustrate the method of measuring the hysteresis characteristics of the soft magnetic material mentioned in the KS standard and the international standard as follows.

(1) device connection

The device is connected as shown in FIG. The DC current source is a battery or a stable DC constant current supply and is connected to the primary (magnetizing) winding N1 of the ring-shaped "test piece" via ammeter A, inverting switch S1 and conversion switch S4.

When switch S5 is closed, the current in the magnetization circuit is regulated by resistor R1. This is the connection of the magnetization circuit to determine the standard magnetization curve and to measure the end point of the hysteresis curve. Switch S5 and resistor R4 are used to obtain a complete hysteresis curve.

In the secondary circuit, the secondary winding N2 (coil B) is connected to the magnetic flux integrator F via the resistor R2 (sensitivity control). Resistor R3 is the class control required for some kind of flux integrator.

(2) Determination of standard magnetization curve

"Test specimens" shall be carefully demagnetized to zero or reverse current gradually by slowly decreasing the direct current at least 10 times the magnetic field strength of the coercive force. When switch S4 is closed in position 2, a small current corresponding to the small magnetic field strength flows through the primary (magnetizing) winding N1.

Invert the current about 10 times with switch S1 to keep the material in a stable cycle. Switch S2 is closed while the flux integrator is operating at zero. When the switch S2 is opened, the magnetic flux integrator value corresponding to the inversion of the magnetic field is recorded and the corresponding magnetic flux density is calculated.

By increasing the magnetization current continuously and repeating this procedure, values corresponding to the strength and magnetic flux density of the magnetic field can be obtained, from which the standard magnetization curve can be obtained. The magnetizing current must never be reduced during the measurement, otherwise it must be demagnetized before the "test piece" can be measured again.

(3) Determination of complete magnetic hysteresis curve

"Test specimen" shall be demagnetized. The end point of the magnetic hysteresis curve is obtained by measuring values corresponding to magnetic field strength and magnetic flux density in accordance with the determination of the standard magnetization curve in (2).

The PQ portion of the magnetic hysteresis curve (in the graph of FIG. 4) is determined by opening switch S5 and measuring the change in magnetic field strength and magnetic flux density when reversal switch S1 reaches position 1.

By adjusting the resistance, many points on the curve PQ can be obtained. Point Q can be obtained by shorting switch S5 and by measuring the change in magnetic flux density when opening switch S1.

The value of the magnetic field strength at each point can be calculated from the measured current flow when switch S5 is opened and resistors R1 and R4 are adjusted to obtain the following values, respectively.

The QS part of the hysteresis curve is determined when the switch S5 is opened. The change in magnetic field strength and magnetic flux density is measured by switch S1 starting in the open position and closing this switch in position 2.

On the other hand, the operation sequence of the switch in the above refer to the right table of FIG.

Since the STUP portion of the curve in the graph of FIG. 4 is symmetrical with the PQRS portion, measurements are usually made only for half of the hysteresis curve.

On the other hand, the important thing in the measurement of the magnetic hysteresis curve is that the magnetic circuit must be manufactured as a closed circuit in order to measure the magnetic characteristics by the ring method.

In this regard, the magnetic shield ring 121, which is a magnetic circuit component in the torque sensor 100, has a structure in which a plurality of windows 121a are formed on a wall thereof by processing a soft magnetic material.

However, in general, it is very difficult to fabricate a soft magnetic steel sheet into a single shielding ring 121 by using a method such as press working, so that the magnetic shield ring 121 has two split rings (as shown in FIG. 2). 121-1 and 121-2) to be manufactured by bending.

As a result, the magnetic shield ring 121, which is a magnetic circuit component manufactured by a conventional general method, cannot take a closed circuit, thereby causing a problem in that magnetic properties of the soft magnetic material cannot be measured.

An object of the present invention is to provide a non-contact torque sensor for a steering apparatus having a magnetic circuit component whose shape is improved to facilitate the measurement of the magnetic properties.

In order to achieve the above object, the present invention, in the non-contact torque sensor for steering apparatus, a magnetic force provided with an upper magnet ring and a lower magnet ring are arranged alternately in the circumferential direction of the plurality of N-pole magnets and S-pole magnets along the outer peripheral surface A generator; Magnetically provided with a plurality of shielding rods disposed at equal intervals corresponding to either the N-pole magnet or the S-pole magnet around the outer periphery of the magnetic force generating unit, and a single connection ring integrally formed with each shielding rod portion. A shield; The magnetic collecting unit is disposed on a radially outer side of the magnetic shield and includes upper and lower magnetic collecting rings for collecting magnetic flux passing through the plurality of shielding rods, and upper and lower magnetic collecting terminals extending from upper and lower magnetic collecting rings. part; And it provides a non-contact torque sensor for the steering apparatus comprising a magnetic detection sensor unit located between the upper and lower collector terminals.

Here, the connection ring may be connected to each one end of the plurality of shielding rod to be made integral.

At this time, the plurality of shielding rod and the connection ring, forming a plurality of shielding rod extending radially to the connection ring and the outside by punching a metal plate of soft magnetic material, and the plurality of shielding rod The inner one end may be bent to be manufactured through a step of forming a shape perpendicular to the connection ring.

Meanwhile, the plurality of shielding rods may be formed to have a width smaller than the width of the N pole and the S pole of the upper to lower magnet rings, respectively.

The plurality of shielding rods and the connection ring may be made of any one of a steel plate, a carbon steel sheet, a silicon steel sheet, and an iron-cobalt alloy steel sheet.

According to the non-contact torque sensor for a steering apparatus according to the present invention, a plurality of shielding rods and connecting rings, which are magnetic circuit components belonging to the magnetic shield, are integrally formed with each other to form a closed circuit, thereby measuring magnetic characteristics thereof.

1 is an exploded perspective view showing a conventional non-contact torque sensor for a steering device;
2 is an enlarged partial exploded perspective view showing some components of the non-contact torque sensor for the steering apparatus of FIG.
3 is a general circuit diagram for obtaining a magnetic history curve which is a magnetic property of a magnetic material;
4 is an operation sequence of the circuit configuration of FIG. 3 and a magnetic history curve obtained through the operation sequence;
5 is an exploded perspective view showing a non-contact torque sensor for a steering apparatus according to an embodiment of the present invention;
6 is a partially exploded perspective view showing the main part of the non-contact torque sensor for the steering apparatus of FIG.
7A and 7B are a plan view and a perspective view for explaining a process of manufacturing a magnetic shield constituting the non-contact torque sensor for the steering apparatus of FIG. 5;
8A and 8B are partially coupled perspective views illustrating the operation of the non-contact torque sensor for the steering apparatus of FIG. 5.

The non-contact torque sensor 200 for the steering apparatus according to the embodiment of the present invention, as shown in Figure 5, the upper magnet ring in which a plurality of N pole magnets and S pole magnets are alternately arranged in the circumferential direction along the outer circumferential surface 211 and the lower magnet ring 212, the magnetic force generating portion 210, the magnetic shield portion 220 disposed around the outer side of the magnetic force generating portion 210, the radially outer side of the magnetic shielding portion 220 It comprises a magnetic collector 230, a magnetic detection sensor 240 for detecting the magnetic force collected from the magnetic collector 230 is disposed in the.

In the present embodiment, the magnetic force generating unit 210 is the same as the corresponding configuration of the preceding invention mentioned in the background art except for some components, the magnetic collecting unit 230 and the magnetic detection sensor unit 240 are respectively It is exactly the same as that of the preceding invention.

The upper magnet ring 211 and the lower magnet ring 212 constituting the magnetic force generating unit 210 are alternately connected to the N pole magnet and the S pole magnet to form a ring shape, and the upper and lower magnet rings 211 and 212, respectively. The magnets of different poles are arranged in the liver (see FIG. 8A).

The magnetic shield 220 includes a soft magnetic material 221 integrally formed with the synthetic resin mold 223 as in the foregoing invention.

As shown in FIG. 6, the soft magnetic material includes a plurality of shielding rods 221 disposed at equal intervals corresponding to either the N pole magnet or the S pole magnet of the magnet ring 211 or 212, It is formed of a single connection ring 222 integrally formed with each shielding rod 221.

In FIG. 6, 233 and 234 are integrally formed from the upper and lower magnetic flux collecting rings 231 and 232 as upper and lower conduit terminals.

In this embodiment, the connection ring 222 is connected to each lower end of the plurality of shielding rod 221 is made integral.

In order to fabricate the structure of the shielding rod 221 and the connection ring 222, by first punching a metal plate made of a soft magnetic material, as shown in Figure 7a and radially extending to the outer connection ring 222 and the outside thereof The plurality of shielding rods 221 are formed, and then the inner ends of the shielding rods 221 are bent, and as shown in FIG. 7B, the molding is completed perpendicular to the connection ring 222.

That is, the molded body of the shielding rod 221 and the connection ring 222 takes a circular closed circuit to measure the magnetic properties thereof.

8A and 8B are diagrams illustrating the positions of main magnetic circuit components according to the operation in order to explain the sensing operation principle of the torque sensor 200 having the structure as described above.

The upper and lower magnet rings 211 and 212 are magnetized in the same number of poles (16 poles in this embodiment), respectively, and are arranged differently in polarity opposite to each other.

A plurality of shielding rods 221 are disposed on the outer circumferential surfaces of the magnet rings 211 and 212 at regular air gaps.

The shielding rod 221 serves as a surface for shielding the magnetic forces of the magnet rings 211 and 212, and a space for passing the magnetic force is formed between the neighboring shielding rods 221.

The shielding rod 221 is formed to have a width smaller than the width of the N pole and the S pole of the magnet rings 211 and 212, and is provided with half the number of poles constituting the magnet rings 211 and 212 (8 in this embodiment). dog).

The upper and lower magnetic flux collecting rings (231 and 232 of FIG. 6) are provided at regular intervals in the axial direction so as to face the upper and lower magnet rings 211 and 212 with a predetermined gap on the outer circumferential surface of the shielding rod 221. .

The operation of the torque sensor 200 having the magnetic circuit as described above is as follows.

First, the torque sensor 200 is a sensor that shows an output value corresponding to the change of the opposite position between the upper and lower magnet rings 211 and 212 connected to the input shaft and the magnetic shields 221 and 222 connected to the output side. .

When the torsion does not occur in the torque sensor 200, as shown in the neutral position of FIG. 8A, the shielding rod 221 is formed on the N and S poles of the upper and lower magnet rings 211 and 212, respectively. It is located at 50.

Therefore, the lines of magnetic force generated in the magnet rings 211 and 212 provided at the top and the bottom flow in the immediately adjacent polarity (N pole-> S pole), and the magnetic flux collecting ring installed at the outer circumferential surface of the shielding rod 221 (Fig. 6). 231, 232) (some amount of micro flows but does not degrade the performance of the sensor will be ignored in this description).

From this neutral state, torsion occurs in accordance with the operating direction of the steering wheel of the vehicle.

On the other hand, the principle of twisting to the left and the principle of twisting to the right are the same, and if the opposite polarities are different, only the sign (+,-) of the output value is different, so here only when twisting occurs in one direction Let's explain.

When the steering wheel of the vehicle is operated, a change in the area that opposes the magnet rings 211 and 212 and the shielding rod 221 occurs.

For example, when the maximum twist occurs, as shown in FIG. 8B, the shielding rod 221 covers the polarities of the inner magnet rings 211 and 212 to the maximum, so that the upper magnet ring 211 has only the N pole. It is transmitted to the magnetic flux collecting ring (231 of FIG. 6) through the space between the shielding rods 221, and the magnetic force of the N pole generated at this time passes through the external Hall sensor (241 of FIG. 5) and is located at the lower magnetic flux. It passes through the collecting ring (232 of FIG. 6) to the S pole of the lower magnet ring 212.

Due to such a flow, a magnetic force is generated around the Hall sensor 241, and an output voltage value corresponding to the magnitude of the magnetic force at this time is output from the Hall sensor 241.

Since the change in area according to the position change between the magnet rings 211 and 212 and the shielding rod 221 increases linearly until the maximum twist occurs in the neutral state, the magnetic force value formed around the Hall sensor 241 is also linear. As a result, the voltage value output from the Hall sensor 241 also changes linearly.

On the other hand, all kinds of magnetic materials have magnetic history characteristics as shown in the graph of Fig. 4 (a).

In general, magnetic materials having coercive force characteristics of less than 1 [kA / m] are called soft magnetic materials. Such soft magnetic materials maintain magnetic force when an external magnetic force is applied, and magnetic properties are removed when the applied magnetic force is removed. Material.

In addition, materials having coercive force characteristics of 1 [kA / m] or more are referred to as hard magnetic materials, and such materials are commonly referred to as permanent magnets.

Hard magnetic material is a material that does not lose the properties of the magnetic force, even if the external magnetic force is removed when the magnetic force is formed from the external magnetic force.

As in the present invention, the torque sensor 200 using the magnetic induction method is a magnetic circuit using permanent magnets (in the present invention, upper and lower magnet rings 211 and 212) and soft magnetic materials, which are hard magnetic materials. (In the present invention, the upper and lower magnetic flux collecting rings 231 and 232 and the collector terminals 233 and 234).

All types of soft magnetic materials are retained when the external magnetic is induced and when the external magnetic is removed, as shown in FIG. 4 (a), a certain amount of residual magnetic force B ₁ remains inside the material, which is zero (0). In order to make it as the external magnetic force (Hc) of any size is applied, the magnitude of the external magnetic force applied at this time is called coercive force.

All types of torque sensors that use soft magnetic materials for magnetic circuits are caused by these coercive force characteristics, resulting in hysteresis characteristics of the sensor. Hysteresis characteristics are different.

The non-contact torque sensor for steering apparatus to which the present invention belongs generally requires low hysteresis characteristics of 1 to 2 [%] levels. In order to satisfy such low hysteresis characteristics, conventional torque sensors are coercive force such as nickel-iron alloy. The hysteresis performance of the sensor required by the system could be satisfied only by using a relatively expensive soft magnetic material with a characteristic of 0.5 to 12 [A / m].

In contrast, the non-contact torque sensor for steering apparatus according to the present invention can be said to be a more flexible structure in the constraint of the material selection.

That is, in the basic structure of the present invention including the magnetic shield 220 consisting of the shielding rod 221 and the connection ring 222 as a magnetic circuit in Figure 6, magnetic collectors 231, 232, 233 and 234 have the limitation of using a soft magnetic material having a coercive force level of 0.5 to 12 [A / m], such as nickel-iron alloy (Permalloy) as in the prior art, but the magnetic shielding and The magnetic shield 220, which only serves as an opening but does not serve as a gyro, can use all kinds of soft magnetic materials without being limited by the coercive force characteristic value of the soft magnetic material. The use of soft magnetic materials is possible.

This can be an important factor in reducing the cost of the entire sensor.

Such soft magnetic materials include steel plates, carbon steel sheets, silicon steel sheets, and iron-cobalt alloy steel sheets.

Here, as the iron plate, a general iron plate, an electrogalvanized steel sheet (SECC), a cold rolled steel sheet (SPCC), etc. may be used.

Considering that the soft magnetic material accounts for 30 to 50 [%] of the total manufacturing cost of the torque sensor, the price of nickel-iron alloy and silicon steel sheet is about 10 times different, so the cost reduction effect is It is very large.

On the other hand, the torque sensor 200 described above is only one embodiment to help the understanding of the present invention, so the scope of the present invention to the technical scope should not be understood to be limited thereto.

The scope of the present invention is defined by the appended claims and their equivalents.

200: torque sensor 210: magnetic force generating unit
211: upper magnet ring 212: lower magnet ring
220: magnetic shield 221: shielding rod
222: connecting ring 223: mold
230: self-collecting unit 231: upper magnetic flux collecting ring
232: lower magnetic flux collecting ring 233: upper magnetic terminal
234: lower house terminal 240: magnetic detection sensor unit
241: Hall sensor

Claims (5)

In the non-contact torque sensor for steering device,
A magnetic force generating unit having an upper magnet ring and a lower magnet ring in which a plurality of N-pole magnets and S-pole magnets are alternately arranged in a circumferential direction along an outer circumferential surface thereof;
Magnetic shield provided with a plurality of shielding rods disposed at equal intervals corresponding to any one of the N-pole magnet and the S-pole magnet around the outer periphery of the magnetic force generating unit, and a single connection ring integrally formed with each shielding rod. Wealth;
The magnetic collecting unit is disposed on a radially outer side of the magnetic shield and includes upper and lower magnetic collecting rings for collecting magnetic flux passing through the plurality of shielding rods, and upper and lower magnetic collecting terminals extending from upper and lower magnetic collecting rings. part; And
It includes a magnetic detection sensor unit located between the upper and lower house terminals,
The connection ring is made integrally connected to each end of the plurality of shielding rods,
The plurality of shielding rod and the connection ring,
Punching a metal plate made of a soft magnetic material to form the connecting ring and the plurality of shielding rods extending radially on the outside thereof, and bending one inner end of each of the plurality of shielding rods to be perpendicular to the connection ring. Non-contact torque sensor for steering apparatus, characterized in that the step is manufactured through. delete delete The method of claim 1,
The plurality of shielding rods are non-contact torque sensor for the steering device, characterized in that formed in a width smaller than the width of the N pole and S pole of the upper to lower magnet ring, respectively. The method of claim 1,
The plurality of shielding rod and the connection ring is a non-contact torque sensor for a steering device, characterized in that made of any one of a steel plate (steel plate), carbon steel sheet, silicon steel sheet, iron-cobalt alloy steel sheet.

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