JP2009139124A - Pulsar ring for magnetic encoders - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a magnetic field required for detecting rotation with high accuracy by a magnetic sensor and excellent corrosion resistance. <P>SOLUTION: A ring shaped holder 11 being attached to the outer circumference of a rotating member and rotating with this rotating member, and a pulsar body 12 bonded to the holder 11 integrally, which is molded with rubber like elastic material mixed with magnetic powder and multipolarly magnetized are provided, wherein the holder 11 consists of a ferritic stainless steel plate containing 20.5-22.0% by mass of Cr, 0.3-0.6% by mass of Cu and 0.1-0.35% by mass of Ti. The holder 11 consisting of the stainless steel plate has a magnetism, and a corrosion resistance equivalent to SUS304. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pulsar ring for a magnetic encoder, and more particularly to a pulsar ring having a structure in which a molded body of a rubber-like elastic material mixed with magnetic powder is joined to a rotating body made of a magnetic metal and multipolarized.

  FIG. 2 is a cross-sectional view of a mounting state in which a conventional magnetic encoder provided integrally with a sealing device for sealing a bearing portion of a wheel suspension device for an automobile is cut along a plane passing through an axis O. In FIG. 2, reference numeral 100 is a sealing device, which is incorporated between the outer ring 201 of the bearing 200 and the end of the inner ring 202 to prevent intrusion of muddy water or the like from the outside of the bearing into the inside of the bearing.

  Specifically, the sealing device 100 includes a metal mounting ring 101 that is press-fitted to the inner peripheral surface of the outer ring 201 of the bearing 200, and a thrust strip that is integrally provided on the mounting ring 101 with a rubber-like elastic material. 102 and a radial lip 103, and a slinger 104 tightly fitted to the outer peripheral surface of the inner ring 202, the tip of the thrust strip 102 is slidably in close contact with the inner surface of the flange 104a of the slinger 104, The inner peripheral edge of the distal end of the radial radial lip 103 is in close contact with the outer peripheral surface of the sleeve portion 104b of the slinger 104 so as to be slidable.

  On the outer surface of the flange 104a of the slinger 104, there is integrally formed a pulsar body 105 which is molded into a disc shape with a magnetic rubber obtained by mixing a rubber-like elastic material with a magnetic material and is multipolarly magnetized at a predetermined pitch in the circumferential direction. The pulsar ring 110 is configured by the pulsar main body 105 and the slinger 104. That is, the slinger 104 serves as a rotary-side sealing element that constitutes the sealing device 100 and also serves as a holder that integrally supports the pulsar body 105 in the pulsar ring 110. In addition, a magnetic sensor 120 is opposed to the outside of the pulsar ring 110 in a non-rotating state. The magnetic sensor 120 constitutes a magnetic encoder together with the pulsar ring 110, and the pulsar ring 110 is a bearing 200. A pulse signal having a waveform corresponding to a change in the magnetic field caused by rotating integrally with the inner ring 202 is generated to detect the rotation.

  However, in this type of pulsar ring 110, SUS430, which is a relatively inexpensive and magnetic ferritic stainless steel, is used as the slinger 104. Since this SUS430 is inferior in corrosion resistance compared to SUS304, it is a region with a lot of rain. In areas close to the sea or the like, there is a problem that rusting occurs on the slinger 104 due to exposure to muddy water or the like, and peeling of the pulsar body 105 is likely to occur.

  For this reason, in order to improve the corrosion resistance of the slinger 104, it is effective to use SUS304. However, since SUS304 is austenitic stainless steel and non-magnetic, it is necessary to be detected by the magnetic sensor 120. It is difficult to obtain a magnetic field and is not functionally suitable as the pulsar ring 110 for a magnetic encoder. Moreover, it has been pointed out that the workability such as deep drawing is worse than that of SUS430, and the material cost is high because it contains expensive Ni and Mo.

Therefore, the slinger 104 is C: 0.025% or less, Si: 1% or less, Mn: 1% or less, P: 0.04% or less, S: 0.01% or less, Ni: 0.6% or less, Cr: 19-21%, Cu : Ferritic stainless steel containing 0.3 to 0.6%, Nb: 10 × (C + N)% or more was developed to improve corrosion resistance and ensure magnetism (see Patent Document 1).
JP 2001-255337 A

  However, the stainless steel plate made of the material described in Patent Document 1 exhibits corrosion resistance superior to that of SUS430, but does not reach SUS304, and thus cannot satisfy the required corrosion resistance.

  The present invention has been made in view of the above points, and the technical problem is that a magnetic field having a required strength for detecting rotation with high accuracy by a magnetic sensor and an excellent It is to ensure corrosion resistance.

  As means for effectively solving the above technical problem, a pulsar ring for a magnetic encoder according to the invention of claim 1 is a rubber-like elastic material in which an annular holder attached to the outer periphery of a rotary member and magnetic powder are mixed. It consists of a pulsar body that is molded with material, multipolar magnetized, and integrally joined to the holder. The holder comprises 20.5 to 22.0 mass% of Cr, 0.3 to 0.6 mass% of Cu, and 0.1 to 0.35 of Ti. It consists of a ferritic stainless steel plate containing mass%.

  In the above configuration, since the holder is made of a ferritic stainless steel plate, it has magnetism, and a magnetic circuit is formed by a magnetic field magnetized on a pulsar body made of a rubber-like elastic material mixed with magnetic powder. For this reason, the strong magnetic field required for the rotation detection by a magnetic sensor is obtained like the case where SUS430 is used.

  In general, a stainless steel sheet exhibits corrosion resistance by forming an oxide film (passive film) with a high Cr density on the surface. However, the ferritic stainless steel sheet forming the holder in the present invention is made of Cr. Depending on the component amounts of Cu, Ti and Ti, even if Ni or Mo is not contained, corrosion resistance substantially equivalent to that of SUS304 is ensured and excellent workability is ensured.

  Specifically, Cr contained in the ferritic stainless steel sheet improves corrosion resistance, and by containing 20.5 mass% or more, corrosion resistance equivalent to SUS304 can be obtained, but when the content exceeds 22.0 mass% Since the toughness of the hot-rolled sheet decreases and the manufacturability deteriorates, the Cr content is set to 20.5 to 22.0 mass%.

  Cu contained in a ferritic stainless steel sheet exhibits the effect of reducing crevice corrosion by containing 0.3 mass% or more, but if the content exceeds 0.6 mass%, hot workability deteriorates, so the inclusion of Cu The amount was 0.3 to 0.6 mass%.

  By containing 0.1 mass% or more of Ti contained in the ferritic stainless steel sheet, the pitting corrosion potential can be increased and the pitting corrosion resistance equivalent to SUS304 can be obtained. However, when the content exceeds 0.35 mass%, the toughness deteriorates remarkably, so the Ti content is set to 0.1 to 0.35 mass%.

  A pulsar ring for a magnetic encoder according to a second aspect of the present invention forms a part of a sealing device when the holder in the above configuration is slidably brought into close contact with a non-rotating seal lip.

  According to the pulsar ring for a magnetic encoder according to the invention of claim 1, since the holder is made of a ferritic stainless steel plate having magnetism, the pulsar body made of a rubber-like elastic material mixed with magnetic powder is stably magnetized. A strong magnetic field can be obtained, and the reliability of rotation detection accuracy can be ensured. In addition, the holder is remarkably superior in corrosion resistance as compared with the one made of SUS430, and even if it does not contain expensive Ni or Mo, the corrosion resistance equivalent to that of SUS304 can be obtained. Can also be improved.

  Moreover, since the ferritic stainless steel sheet forming the holder has a lower density than SUS304, it is possible to reduce the weight and reduce the rotational torque. Furthermore, since the thermal expansion coefficient is smaller than that of SUS304, As a result, the magnetic field does not become unstable due to the change of the thermal environment, and the reliability of the rotation detection accuracy can be ensured.

  According to the pulsar ring for the magnetic encoder according to the invention of claim 2, when the holder forms a part of the sealing device and is slidably in close contact with the seal lip, it is rusted even when exposed to muddy water or salt water. It is possible to effectively prevent the pulsar body from being peeled off due to the occurrence of wear and the wear due to the corrosion of the sliding surface with the seal lip. Moreover, since the ferritic stainless steel plate forming the holder has a higher thermal conductivity than SUS304, heat generated by sliding with the seal lip is easily released. As a result, the durability of the seal lip and the seal Sex is secured.

  Hereinafter, a pulsar ring for a magnetic encoder according to the present invention will be described with reference to the drawings.

  FIG. 1 is a partial cross-sectional perspective view showing a preferred embodiment of a pulsar ring for a magnetic encoder according to the present invention. A pulsar ring 10 shown in FIG. 1 is an annular holder attached to the outer periphery of a rotating side member. 11 and a pulsar main body 12 provided integrally with the holder 11.

  The holder 11 has a substantially L-shaped shape cut by a plane passing through the shaft center. That is, the holder 11 includes an attachment tube portion 11a and a flange portion 11b extending in a disk shape from one end in the axial direction to the outer peripheral side.

  The pulsar body 12 is integrally formed on the outer surface of the flange portion 11b of the holder 11 (the surface opposite to the protruding direction of the mounting tube portion 11a), and is made of synthetic resin or rubber mixed with magnetic powder. It is a disc-shaped multipolar magnet made of an elastic material and having S poles and N poles alternately magnetized at a predetermined pitch in the circumferential direction.

  The holder 11 is manufactured by punching and pressing a ferritic stainless steel plate containing 20.5 to 22.0 mass% of Cr, 0.3 to 0.6 mass% of Cu, and 0.1 to 0.35 mass% of Ti.

  In the magnetic encoder pulsar ring 10 configured as described above, the holder 11 is attached to the outer periphery of a rotating body (not shown) (for example, a rotating shaft or an inner ring of a bearing) by means such as press fitting in the mounting cylinder portion 11a. And rotates integrally with the rotating body. On the other hand, a magnetic sensor (not shown) is arranged in a non-rotating state so as to face the pulsar main body 12 in the axial direction, and the front surface of the detection surface of the magnetic sensor is rotated integrally with the rotating body. By alternately passing the N pole and S pole magnetized in the pulsar body 12 in the rotation direction, a pulsed signal with a waveform corresponding to the change in the magnetic field is output, thereby measuring the rotation angle and rotation speed. can do.

  Moreover, this pulsar ring 10 can also serve as the rotation side sealing element (slinger) of the sealing device 100 as in FIG. 2 described above. That is, in this case, the tip of the thrust strip 102 shown in FIG. 2 is slidably brought into close contact with the surface (inner surface) on the opposite side (inner surface) of the flange portion 11b of the holder 11 to the pulsar body 12. The inner peripheral edge of the distal end of the radial lip 103 on the peripheral side is brought into close contact with the outer peripheral surface of the mounting cylinder portion 11a of the holder 11 so as to be slidable.

Table 1 shows examples of ferritic stainless steel plates of 21 mass% Cr, 0.4 mass% Cu, 0.3 mass% Ti, the balance Fe and other minute metals and inevitable impurities, and other materials ( In the stainless steel plates of Comparative Examples 1 to 3, the pitting corrosion potential, ease of drawing, presence / absence of magnetism, density, thermal expansion coefficient, and thermal conductivity are shown in comparison. The stainless steel plate of Comparative Example 1 is SUS430 and contains 16.1 mass% Cr, and the stainless steel plate of Comparative Example 2 is SUS304, which contains 18.2 mass% Cr and 8.2 mass% Ni. The stainless steel plate of Comparative Example 3 is SUS430J1L, which is substantially equivalent to the material disclosed in Patent Document 1 described above as the prior art, and Cr is 19.2 mass%, Cu is 0.5 mass%, and Nb is 0.4 mass%. Contains.

  Here, the pitting potential is a critical potential at which pore-like local corrosion (pitting corrosion) occurs on the surface of a stainless steel plate passivated by an oxide film, and the higher this value, the higher the corrosion resistance. And according to Table 1, the pitting corrosion potential of the stainless steel plate of the example is much higher than that of Comparative Example 1 (SUS430), and the Cr content is 19.2 mass% and does not contain Ti. 1 is sufficiently higher than Comparative Example 3 (SUS430J1L) substantially corresponding to 1, and shows a high value equivalent to Comparative Example 2 (SUS304). Therefore, it turns out that it has the outstanding corrosion resistance comparable to SUS304.

  The r value (Rankford value) is the ratio of the strain in the width direction to the strain in the plate thickness direction when tensile deformation is applied to a material having plastic anisotropy. Good sex. And according to Table 1, it turns out that the stainless steel plate of an Example has an average r value higher than the comparative example 1 and the comparative example 2, ie, has the workability superior to SUS430 and SUS304. For this reason, the holder 11 having a cross-sectional shape as shown in FIG. 1 can be easily formed by deep drawing.

  Moreover, it turns out that the ferritic stainless steel plate of an Example has a density lower than the comparative example 2 (SUS304), a small thermal expansion coefficient, and high thermal conductivity.

1 is a partial sectional perspective view showing a preferred embodiment of a pulsar ring for a magnetic encoder according to the present invention by cutting along a plane passing through an axis O. FIG. It is sectional drawing of the mounting state which shows the conventional magnetic encoder integrally provided in the sealing device which seals the bearing part of the wheel suspension apparatus for motor vehicles cut | disconnected by the plane which passes along an axial center.

Explanation of symbols

10 Pulsar ring 11 Holder 12 Pulsar body

Claims (2)

  An annular holder attached to the outer periphery of the rotating side member, and a pulsar main body molded with a rubber-like elastic material mixed with magnetic powder and multipolarly magnetized and integrally joined to the holder, A pulsar ring for a magnetic encoder, comprising a ferritic stainless steel plate containing 20.5 to 22.0 mass% of Cr, 0.3 to 0.6 mass% of Cu, and 0.1 to 0.35 mass% of Ti.   The pulsar ring for a magnetic encoder according to claim 1, wherein the holder forms a part of a sealing device by being slidably brought into close contact with a non-rotating seal lip.

Images